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JP2015184067

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DESCRIPTION JP2015184067
Abstract: A wide dynamic range pressure sensor, a microphone and an acoustic processing
system, or a pressure sensor, a microphone and an acoustic processing system capable of
detecting in a wide frequency band are provided. A pressure sensor is provided that includes a
substrate, a sensor unit, and a processing circuit. The sensor unit includes a transducing thin
film, a first strain sensing element, and a second strain sensing element. The transducing thin
film has a film surface and is flexible. The first strain sensing element is provided on the film
surface at a position different from the center of gravity of the film surface. The second strain
sensing element is provided on the film surface at a position separated from the first strain
sensing element and different from the center of gravity. The processing circuit is configured to
generate a first signal obtained from the first strain sensing element when an external pressure is
applied to the transducing thin film and a second signal obtained from the second strain sensing
element when an external pressure is applied to the transducing thin film One of the two signals
is output as an output signal. [Selected figure] Figure 1
Pressure sensor, microphone and sound processing system
[0001]
Embodiments of the present invention relate to pressure sensors, microphones and sound
processing systems.
[0002]
In a capacitive microphone that converts sound into an electrical signal by a change in
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capacitance, the entire diaphragm becomes part of the electrode.
Therefore, as the microphone is miniaturized, the area of the electrode is reduced along with the
diaphragm, and the sensitivity is degraded. On the other hand, the sensitivity is improved by
reducing the gap between the capacitors. However, if the gap between the capacitors is reduced,
the gap between the capacitors may not be sufficient at high volume, which may cause sticking
of the diaphragm to the electrode. In addition, in the capacitive microphone, even if it is possible
to cope with a large volume by providing a plurality of diaphragms, switching of the diaphragms
may be difficult for high frequency sound.
[0003]
JP, 2013-205403, A
[0004]
Embodiments of the present invention provide a wide dynamic range pressure sensor
microphone and sound processing system, or a pressure sensor, microphone and sound
processing system that can be detected in a wide frequency band.
[0005]
According to an embodiment, a pressure sensor is provided that includes a substrate, a sensor
unit, and a processing circuit.
The sensor unit is provided on the base.
The processing circuit processes a signal obtained from the sensor unit. The sensor unit includes
a transducing thin film, a first strain sensing element, and a second strain sensing element. The
transducing thin film has a film surface and is flexible. The first strain sensing element is
provided on the film surface at a position different from the center of gravity of the film surface.
The second strain sensing element is provided at a position apart from the first strain sensing
element on the film surface and at a position different from the center of gravity. The processing
circuit is configured to generate a first signal obtained from the first strain sensing element when
an external pressure is applied to the transducing thin film, and a second signal when the
external pressure is applied to the transducing thin film. One of the second signals obtained from
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the sensing elements is output as an output signal.
[0006]
It is a typical perspective view showing a pressure sensor concerning a 1st embodiment. It is a
schematic plan view showing a part of pressure sensor concerning a 1st embodiment. Fig.3 (a)FIG.3 (d) are typical top views which show a part of pressure sensor which concerns on 1st
Embodiment. It is a typical perspective view showing a part of pressure sensor concerning a 1st
embodiment. FIG. 5A to FIG. 5C are schematic perspective views showing the operation of the
pressure sensor according to the first embodiment. FIG. 6A and FIG. 6B are schematic
perspective views showing a part of the pressure sensor according to the first embodiment. FIG.
7A and FIG. 7B are schematic views showing the operation of the pressure sensor according to
the first embodiment. FIGS. 8A and 8B are schematic views showing the relationship between the
position on the film surface of the transducing thin film and the strain. FIGS. 9A and 9B are
schematic views showing the relationship between the position on the film surface of another
transducing thin film and the strain. FIG. 10 is a graph showing the optimum strain range of the
strain sensing element. FIG. 11A and FIG. 11B are schematic plan views showing an example of
the pressure sensor according to the present embodiment. FIG. 12A to FIG. 12C are schematic
views showing an example of connection of sensor lines according to the present embodiment.
FIG. 13A and FIG. 13B are schematic plan views showing an example of the pressure sensor
according to the present embodiment. FIGS. 14 (a) and 14 (b) are schematic diagrams showing
the circuit after the output of the line. FIGS. 15 (a) and 15 (b) are flowcharts illustrating a method
of generating a control signal. FIG. 16A and FIG. 16B are flowcharts showing the operation of the
pressure sensor according to the first embodiment. It is a schematic plan view which shows
another pressure sensor which concerns on 2nd Embodiment. It is a schematic plan view which
shows another pressure sensor which concerns on 2nd Embodiment. It is a schematic plan view
which shows another pressure sensor which concerns on 2nd Embodiment. It is a flowchart
figure which shows the manufacturing method of the pressure sensor concerning a 3rd
embodiment. FIG. 21A to FIG. 21D are schematic perspective views in order of steps showing a
method of manufacturing a pressure sensor according to a third embodiment. It is a schematic
diagram explaining the confirmation process in the manufacturing method of the pressure sensor
which concerns on 3rd Embodiment. FIGS. 23 (a) and 23 (b) are schematic diagrams showing an
example in which one of a plurality of lines is fixed and output. It is a typical perspective view
showing a pressure sensor concerning a 4th embodiment. 25 (a) to 25 (c) are schematic views
showing a pressure sensor according to a fourth embodiment.
It is a flowchart figure which shows the manufacturing method of the pressure sensor which
concerns on 5th Embodiment. It is a schematic diagram which shows the microphone which
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concerns on 6th Embodiment.
[0007]
Hereinafter, each embodiment will be described with reference to the drawings. The drawings are
schematic or conceptual, and ratios of sizes among parts are not necessarily the same as real
ones. In addition, even in the case of representing the same portion, the dimensions and ratios
may be different from one another depending on the drawings. In the specification of the present
application and the drawings, the same elements as those described above with reference to the
drawings are denoted by the same reference numerals, and the detailed description will be
appropriately omitted.
[0008]
First Embodiment FIG. 1 is a schematic perspective view illustrating the configuration of a
pressure sensor according to a first embodiment. In FIG. 1, in order to make a figure legible, an
insulation part is omitted and a conductive part is mainly drawn. FIG. 2 is a schematic plan view
illustrating the configuration of a part of the pressure sensor according to the first embodiment.
[0009]
As shown in FIG. 1, the pressure sensor 310 according to the present embodiment includes a
base 71 a and a sensor unit 72 (first sensor unit 72 </ b> A). The sensor unit 72 is provided on
the base 71 a. The sensor unit 72 (first sensor unit 72A) includes a first transducing thin film
64A and a first strain sensing element 50A. The first transducing thin film 64A has a film surface
64a (first film surface). The first transducing thin film 64A is flexible. The first transducing thin
film 64A has a function of bending when a pressure is applied from the outside and transducing
the strain sensing element 50 formed thereon as a strain. The external pressure may be a
pressure itself or a pressure by sound waves or ultrasonic waves. In the case of sound or
ultrasound, the pressure sensor will function as a microphone.
[0010]
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In some cases, the thin film to be the transducing thin film 64 is continuously formed outside the
portion bent by the external pressure. In the specification of the present application, a portion
surrounded by the fixed end, which is thinner than the fixed end with a certain thickness and is
flexed by the external pressure, is called a transducing thin film.
[0011]
The first transducing thin film 64A is fixed to the base 71a at the edge 64eg. The first strain
sensing element 50A is provided on the first film surface. The configuration of the first strain
sensing element 50A will be described later.
[0012]
A cavity 70 is formed in the base 71a. The portion other than the hollow portion 70 in the base
71 a corresponds to the non-hollow portion 71. The non-cavity 71 is juxtaposed with the cavity
70.
[0013]
The hollow portion 70 is a portion where the material forming the non-hollow portion 71 is not
provided. The inside of the cavity 70 may be a vacuum (a low pressure state lower than 1 atm),
and the cavity 70 may be filled with a gas such as air or an inert gas. Further, the hollow portion
70 may be filled with a liquid. A deformable material may be disposed in the hollow portion 70
so that the first transducer thin film 64A can bend.
[0014]
When pressure (including sound, ultrasonic waves, and the like) is applied to the first
transducing thin film 64A from the outside, the first transducing thin film 64A is bent. Along
with this, distortion occurs in the strain sensor (sensor unit 72) disposed on the first transducing
thin film 64A. Thus, the first transducing thin film 64A transmits (transduces) a signal of
pressure to the sensor unit 72, and the signal of pressure is converted to a signal of distortion in
the sensor unit 72.
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[0015]
The first transducing thin film 64A is disposed above the cavity 70 and fixed to the base 71a at
the edge 64eg.
[0016]
Here, a plane parallel to the film surface 64a (first film surface) is taken as an XY plane.
When the film surface 64a is not a flat surface, a plane including the edge 64eg of the film
surface 64a is taken as an XY plane. The direction perpendicular to the X-Y plane is taken as the
Z-axis direction.
[0017]
As shown in FIGS. 1 and 2, in the pressure sensor 310, the base 71a, the transducing thin film 64
(first transducing thin film 64A), the first strain sensing element 50A, the first wiring 57 (wirings
57a to 57d) and Second wires 58 (wires 58a to 58d) are provided. In this example, a plurality of
strain sensing elements 50 (strain sensing elements 50a to 50d) are provided. The first strain
sensing element 50A is any one of the plurality of strain sensing elements 50. For example, the
strain sensing element 50a is used as the first strain sensing element 50A.
[0018]
That is, the sensor unit 72 (first sensor unit 72A) further includes the second strain sensing
element 50B. The second strain sensing element 50B is provided on the film surface 64a. For
example, the strain sensing element 50b is used as the second strain sensing element 50B. In this
example, a straight line passing through the first strain sensing element 50A and the second
strain sensing element 50B passes the center of gravity 64b of the film surface 64a. Specifically,
a straight line passing the center of gravity of the first strain sensing element 50A and the center
of gravity of the second strain sensing element 50B passes the center of gravity 64b. The
distance between the first strain sensing element 50A and the center of gravity 64b of the film
surface 64a is different from the distance between the second strain sensing element 50B and
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the center of gravity 64b of the film surface 64a.
[0019]
The sensor unit 72 further includes a third strain sensing element 50C. The third strain sensing
element 50C is provided on the film surface 64a. For example, the strain sensing element 50c is
used as the third strain sensing element 50C. In this example, a straight line passing through the
first strain sensing element 50A, the second strain sensing element 50B, and the third strain
sensing element 50C passes the center of gravity 64b of the film surface 64a. Specifically, a
straight line passing the center of gravity of the first strain sensing element 50A, the center of
gravity of the second strain sensing element 50B, and the center of gravity of the third strain
sensing element 50C passes through the center of gravity 64b. The distance between the third
strain sensing element 50C and the center of gravity 64b of the film surface 64a is the distance
between the first strain sensing element 50A and the center of gravity 64b of the film surface
64a and the distance between the second strain sensing element 50B and the film surface 64a. It
is different from the distance between the center of gravity 64b.
[0020]
The sensor unit 72 further includes a fourth strain sensing element 50D. The fourth strain
sensing element 50D is provided on the film surface 64a. For example, a strain sensing element
50d is used as the fourth strain sensing element 50D. In this example, a straight line passing
through the first strain sensing element 50A, the second strain sensing element 50B, the third
strain sensing element 50C, and the fourth strain sensing element 50D passes the center of
gravity 64b of the film surface 64a. Specifically, a straight line passing the center of gravity of
the first strain sensing element 50A, the center of gravity of the second strain sensing element
50B, the center of gravity of the third strain sensing element 50C, and the center of gravity of the
fourth strain sensing element 50D is It passes the center of gravity 64b. The distance between
the fourth strain sensing element 50D and the center of gravity 64b of the film surface 64a is the
distance between the first strain sensing element 50A and the center of gravity 64b of the film
surface 64a, and the distance between the second strain sensing element 50B and the film
surface 64a The distance between the center of gravity 64b and the distance between the third
strain sensing element 50C and the center of gravity 64b of the film surface 64a are different.
[0021]
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In this example, four strain sensing elements 50 (strain sensing elements 50a to 50d) are
provided. The strain sensing elements 50a to 50d are arranged along the portion on the −X axis
direction side from the center (corresponding to the gravity center 64b) in the straight line 64d
on the film surface 64a. The strain sensing element 50 is disposed at a position different from
the position of the center of gravity 64 b of the film surface 64 a of the transducing thin film 64.
The number of strain sensing elements 50 installed is not limited to four. The number of strain
sensing elements 50 may be plural, and may be two, three, or five or more.
[0022]
FIG. 3A to FIG. 3D are schematic plan views illustrating the configuration of part of the pressure
sensor according to the first embodiment. These figures illustrate the shape of the film surface
64 a of the transducing thin film 64. As shown in FIGS. 3A to 3D, the shape of the film surface
64a (a bending portion) of the transducing thin film 64 is a circle, a flat circle (including an
ellipse), a square or a rectangle, etc. . In such a case, the center of gravity of the film surface 64a
is the center of a circle, the center of an ellipse, the center of a diagonal of a square, or the center
of a diagonal of a rectangle.
[0023]
The transducing thin film 64 is formed of, for example, an insulating layer. Alternatively, the
transducing thin film 64 is formed of, for example, a metal material. The transducing thin film 64
includes, for example, silicon oxide or silicon nitride. The thickness of the transducing thin film
64 is, for example, 200 nm or more and 3 μm or less. Preferably, it is 300 nm or more and 1.5
μm or less. The diameter of the transducing thin film 64 is, for example, 1 μm or more and 600
μm or less. More preferably, they are 60 micrometers or more and 600 micrometers or less. The
transducing thin film 64 is, for example, flexible in the Z-axis direction perpendicular to the film
surface 64a.
[0024]
As shown in FIG. 2, in this example, the straight line 64c passes the center of gravity 64b of the
film surface 64a of the transducing thin film 64 and is parallel to the Y-axis direction. The
straight line 64 d passes through the center of gravity 64 b of the film surface 64 a of the
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transducing thin film 64 and is parallel to the X-axis direction. When the same material is used
for the transducing thin film 64 and the substrate 71 a and they are integrated, the edge of the
thin portion becomes the edge 64 eg of the transducing thin film 64. When the transducing thin
film 64 has the cavity 70 penetrating the base 71 a in the thickness direction and the
transducing thin film 64 is provided to cover the cavity 70, the transducing thin film 64 is
formed. Of the material film, the edge of the portion overlapping the cavity 70 is the edge 64eg
of the transducing thin film 64.
[0025]
One end of each of the strain sensing elements 50 a to 50 d is connected to each of the first
wires 57 (for example, the wires 57 a to 57 d). The other end of each of the strain sensing
elements 50a to 50d is connected to each of the second wires 58 (for example, 58a to 58d).
[0026]
The first wire 57 and the second wire 58 extend from the strain sensing element 50 toward the
base 71 a through the edge 64 eg.
[0027]
FIG. 4 is a schematic perspective view illustrating the configuration of part of the pressure sensor
according to the first embodiment.
FIG. 4 shows an example of the configuration of the strain sensing element 50. As shown in FIG.
As shown in FIG. 3, the strain resistance change unit 50s (the strain sensing element 50, the first
strain sensing element 50A) includes, for example, the first magnetic layer 10, the second
magnetic layer 20, and the first magnetic layer. And an intermediate layer 30 (first intermediate
layer) provided between the second magnetic layer 20 and the second magnetic layer 20. The
intermediate layer 30 is a nonmagnetic layer. The configuration of each of the plurality of strain
sensing elements 50 is also similar to that described above.
[0028]
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In this example, the first magnetic layer 10 is a magnetization free layer. The second magnetic
layer 20 is, for example, a magnetization fixed layer or a magnetization free layer.
[0029]
Hereinafter, an example of the operation of the strain sensing element 50 will be described in the
case where the second magnetic layer 20 is a magnetization fixed layer and the first magnetic
layer 10 is a magnetization free layer. In the strain sensing element 50, the “inverse
magnetostrictive effect” of the ferromagnetic material and the “MR effect” exhibited in the
strain resistance change portion 50s are used.
[0030]
The “MR effect” is a phenomenon in which in the laminated film having a magnetic body,
when an external magnetic field is applied, the value of the electrical resistance of the laminated
film changes due to the change in the magnetization of the magnetic body. The MR effect
includes, for example, a GMR (Giant magnetoresistance) effect or a TMR (Tunneling
magnetoresistance) effect. By supplying a current to the strain resistance change unit 50s, the
MR effect is expressed by reading the change in the relative angle of the magnetization direction
as the change in electrical resistance. For example, based on the stress applied to the strain
sensing element 50, a tensile stress is applied to the strain resistance change portion 50s. When
the direction of the magnetization of the first magnetic layer 10 (the magnetization free layer)
and the direction of the tensile stress applied to the second magnetic layer 20 are different from
each other, the MR effect is exhibited due to the inverse magnetostrictive effect. Assuming that
the resistance in the low resistance state is R and the amount of change in electrical resistance
that changes due to the MR effect is ΔR, ΔR / R is called “MR change rate”.
[0031]
FIG. 5A to FIG. 5C are schematic perspective views illustrating the operation of the pressure
sensor according to the first embodiment. These drawings illustrate the state of the strain
sensing element 50. These drawings illustrate the relationship between the magnetization
direction in the strain sensing element 50 and the direction of tensile stress.
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[0032]
FIG. 5A shows a state in which no tensile stress is applied. At this time, in this example, the
direction of the magnetization of the second magnetic layer 20 (the magnetization fixed layer) is
the same as the direction of the magnetization of the first magnetic layer 10 (the magnetization
free layer).
[0033]
FIG. 5 (b) shows a state in which a tensile stress is applied. In this example, tensile stress is
applied along the X-axis direction. For example, the deformation of the transducing thin film 64
applies, for example, a tensile stress along the X-axis direction. That is, the tensile stress is
applied in a direction orthogonal to the magnetization directions (in this example, the Y-axis
direction) of the second magnetic layer 20 (the magnetization fixed layer) and the first magnetic
layer 10 (the magnetization free layer). At this time, the magnetization of the first magnetic layer
10 (the magnetization free layer) is rotated so as to be in the same direction as the direction of
the tensile stress. This is called "inverse magnetostriction effect". At this time, the magnetization
of the second magnetic layer 20 (the magnetization fixed layer) is fixed. Therefore, the
magnetization of the first magnetic layer 10 (magnetization free layer) is rotated, whereby the
direction of magnetization of the second magnetic layer 20 (magnetization fixed layer) and the
direction of magnetization of the first magnetic layer 10 (magnetization free layer) are obtained.
The relative angle between and changes.
[0034]
In this drawing, the magnetization direction of the second magnetic layer 20 (the magnetization
fixed layer) is illustrated as an example, and the magnetization direction may not be the direction
shown in this drawing.
[0035]
In the inverse magnetostrictive effect, the easy axis of magnetization changes depending on the
sign of the magnetostriction constant of the ferromagnetic body.
Many materials that exhibit large inverse magnetostrictive effects have positive magnetostriction
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constants. When the magnetostriction constant is a positive sign, as described above, the
direction in which the tensile stress is applied is the easy magnetization axis. At this time, as
described above, the magnetization of the first magnetic layer 10 (the magnetization free layer)
rotates in the direction of the magnetization easy axis.
[0036]
For example, when the magnetostriction constant of the first magnetic layer 10 (magnetization
free layer) is positive, the magnetization direction of the first magnetic layer 10 (magnetization
free layer) is set to a direction different from the direction in which tensile stress is applied. . On
the other hand, when the magnetostriction constant is negative, the direction perpendicular to
the direction in which the tensile stress is applied is the easy magnetization axis.
[0037]
FIG. 5C exemplifies a state where the magnetostriction constant is negative. In this case, the
magnetization direction of the first magnetic layer 10 (magnetization free layer) is set to a
direction different from the direction perpendicular to the direction in which tensile stress is
applied (in this example, the X-axis direction).
[0038]
In this drawing, the magnetization direction of the second magnetic layer 20 (the magnetization
fixed layer) is illustrated as an example, and the magnetization direction may not be the direction
shown in this drawing.
[0039]
Depending on the angle between the magnetization of the first magnetic layer 10 and the
magnetization of the second magnetic layer 20, the electrical resistance of the strain sensing
element 50 (the strain resistance change unit 50s) changes, for example, due to the MR effect.
[0040]
The magnetostriction constant (λs) indicates the magnitude of the change in shape when the
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external magnetic field is applied to saturate the ferromagnetic layer in a certain direction.
Assuming that the length is L in the absence of an external magnetic field, the magnetostriction
constant λs is represented by ΔL / L, assuming that it changes by ΔL when the external
magnetic field is applied.
The amount of change varies depending on the magnitude of the magnetic field, but the
magnetostriction constant λs is expressed as ΔL / L in a state where the sufficient magnetic
field is applied and the magnetization is saturated.
[0041]
For example, when the second magnetic layer 20 is a magnetization fixed layer, Fe, Co, Ni, or
their alloy materials are used for the second magnetic layer 20. For the second magnetic layer
20, a material obtained by adding an additive element to the above-described material is used.
For the second magnetic layer 20, for example, a CoFe alloy, a CoFeB alloy, a NiFe alloy or the
like can be used. The thickness of the second magnetic layer 20 is, for example, not less than 2
nanometers (nm) and not more than 6 nm.
[0042]
For the intermediate layer 30, a metal or an insulator can be used. As the metal, for example, Cu,
Au, Ag or the like can be used. In the case of metal, the thickness of the intermediate layer 30 is,
for example, 1 nm or more and 7 nm or less. As the insulator, for example, magnesium oxide
(such as MgO), aluminum oxide (such as Al2O3), titanium oxide (such as TiO), and zinc oxide
(such as ZnO) can be used. In the case of an insulator, the thickness of the intermediate layer 30
is, for example, 1 nm or more and 3 nm or less.
[0043]
When the first magnetic layer 10 is a magnetization free layer, for example, an alloy material
containing at least one of Fe, Co, and Ni, or at least one of them is used for the first magnetic
layer 10. The material which added the additional element to said material is used.
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[0044]
For the first magnetic layer 10, a material having a large magnetostriction is used. Specifically, a
material whose absolute value of magnetostriction is larger than 10 <-5> is used. Thereby, the
magnetization is sensitive to strain. For the first magnetic layer 10, a material having positive
magnetostriction may be used, or a material having negative magnetostriction may be used.
[0045]
For the first magnetic layer 10, for example, a FeCo alloy, a NiFe alloy or the like can be used.
Besides, in the first magnetic layer 10, an Fe--Co--Si--B alloy, a Tb-M--Fe alloy showing λs> 100
ppm (M is Sm, Eu, Gd, Dy, Ho, Er), Tb- M1-Fe-M2 alloy (M1 is Sm, Eu, Gd, Dy, Ho, Er, M2 is Ti, Cr,
Mn, Co, Cu, Nb, Mo, W, Ta), Fe-M3-M4- B alloy (M3 is Ti, Cr, Mn, Co, Cu, Nb, Mo, W, Ta, M4 is Ce,
Pr, Nd, Sm, Tb, Dy, Er), Ni, Al-Fe or ferrite Fe3O4, (FeCo) 3O4) and the like can be used. The
thickness of the first magnetic layer 10 is, for example, 2 nm or more.
[0046]
The first magnetic layer 10 can have a two-layer structure. In this case, the first magnetic layer
10 can include a layer of FeCo alloy, and the following layers stacked with a layer of FeCo alloy.
An Fe-Co-Si-B alloy, a Tb-M-Fe alloy showing λs> 100 ppm (M is Sm, Eu, Gd, Dy, Ho, Er), Tblaminated with a layer of FeCo alloy M1-Fe-M2 alloy (M1 is Sm, Eu, Gd, Dy, Ho, Er, M2 is Ti, Cr,
Mn, Co, Cu, Nb, Mo, W, Ta), Fe-M3-M4- B alloy (M3 is Ti, Cr, Mn, Co, Cu, Nb, Mo, W, Ta, M4 is Ce,
Pr, Nd, Sm, Tb, Dy, Er), Ni, Al-Fe or ferrite It is a layer of a material selected from Fe3O4, (FeCo)
3O4) and the like.
[0047]
For example, when the intermediate layer 30 is a metal, the GMR effect appears. When the
intermediate layer 30 is an insulator, the TMR effect is exhibited. For example, in the strain
sensing element 50, for example, a CPP (Current Perpendicular to Plane) -GMR effect of causing
a current to flow along the stacking direction of the strain resistance change unit 50s is used.
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[0048]
Further, a CCP (Current-Confined-Path) spacer layer in which a plurality of metal current paths
having a width (for example, diameter) of about 1 nm or more and 5 nm are penetrated in part in
the insulating layer as the intermediate layer 30 is formed. Can be used. Again, the CCP-GMR
effect is used.
[0049]
Thus, in the present embodiment, the inverse magnetostriction phenomenon in the strain sensing
element 50 is used. This enables highly sensitive detection. When the inverse magnetostrictive
effect is used, for example, the magnetization direction of at least one of the first magnetic layer
10 and the second magnetic layer 20 changes with respect to externally applied strain. The
relative angle between the magnetizations of the two magnetic layers changes depending on the
externally applied strain (such as the presence or absence and the degree thereof). The strain
sensing element 50 functions as a pressure sensor because the electrical resistance is changed by
externally applied strain.
[0050]
FIG. 6A and FIG. 6B are schematic perspective views illustrating the configuration of part of the
pressure sensor according to the first embodiment. As illustrated in FIG. 6A, the strain sensing
element 50 includes, for example, a first electrode 51 and a second electrode 52. The strain
resistance change unit 50 s is provided between the first electrode 51 and the second electrode
52. In this example, in the strain resistance change unit 50s, the buffer layer 41 (also serving as a
seed layer may be provided from the side of the first electrode 51 toward the second electrode
52. The thickness is, for example, 1 nm or more and 10 nm or less. Specifically, an amorphous
layer containing Ta or Ti or the like is used, and a layer such as Ru or NiFe which is a seed layer
for promoting crystal orientation is used. The laminated film may be used), the antiferromagnetic
layer 42 (for example, thickness 5 nm or more and 10 nm or less), the magnetic layer 43 (for
example, thickness 2 nm or more and 6 nm or less), the Ru layer 44, the second magnetic layer
20 (for example The thickness is 2 nm to 5 nm), the intermediate layer 30 (eg, thickness 1 nm to
3 nm), the first magnetic layer 10 (eg, thickness 2 nm to 5 nm), and the cap layer 45 (eg,
thickness 1 nm to 5 nm) It is provided in this order.
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[0051]
For the second magnetic layer 20, for example, a magnetic laminated film is used. The first
magnetic layer 10 is a magnetic laminated film 10 a (for example, having a thickness of 1 nm or
more and 3 nm or less) for increasing the MR ratio. For example, an alloy containing CoFe, CoFe,
or the like is used, and a high magnetostrictive magnetic film 10 b (for example, 1 nm or more
and 5 nm or less) provided between the magnetic laminated film 10 a and the cap layer 45.
[0052]
For the first electrode 51 and the second electrode 52, for example, Au, Cu, Ta, Al or the like
which is a nonmagnetic material can be used. By using a soft magnetic material as the first
electrode 51 and the second electrode 52, it is possible to reduce external magnetic noise
affecting the strain resistance change portion 50s. As a material of the soft magnetic body, for
example, permalloy (NiFe alloy) or silicon steel (FeSi alloy) can be used. The strain sensing
element 50 is covered with an insulator such as aluminum oxide (e.g. Al2O3) or silicon oxide (e.g.
SiO2) to prevent leakage current from flowing around.
[0053]
The magnetization direction of at least one of the first magnetic layer 10 and the second
magnetic layer 20 changes in accordance with the stress. The absolute value of the
magnetostriction constant of at least one of the magnetic layers (the magnetic layer whose
magnetization direction changes according to stress) is preferably set to, for example, 10 <−5>
or more. Thereby, the magnetization direction changes in accordance with the externally applied
strain due to the inverse magnetostrictive effect. For example, for at least one of the first
magnetic layer 10 and the second magnetic layer 20, a metal such as Fe, Co, Ni, or the like, an
alloy containing them, or the like is used. The magnetostriction constant is set large depending
on the element to be used, the additive element, and the like. The absolute value of the
magnetostriction constant is preferably large. Considering the material that can be used as a
realistic device, the absolute value of the magnetostriction constant is practically 10 <-2> or less.
[0054]
04-05-2019
16
For example, an oxide such as MgO is used as the intermediate layer 30. The magnetic layer on
the MgO layer generally has a positive magnetostriction constant. For example, when the first
magnetic layer 10 is formed on the intermediate layer 30, a magnetization free layer having a
stacked structure of CoFeB / CoFe / NiFe is used as the first magnetic layer 10. When the
uppermost NiFe layer is made Ni-rich, the magnetostriction constant of the NiFe layer is negative
and its absolute value becomes large. In order to suppress the cancellation of the positive
magnetostriction on the oxide layer, the Ni composition of the uppermost NiFe layer is not made
rich in Ni as compared with the permalloy composition of Ni81 Fe19 which is generally used.
Specifically, the ratio of Ni in the uppermost NiFe layer is preferably less than 80 atomic percent
(atomic%). When the first magnetic layer 10 is a magnetization free layer, the thickness of the
first magnetic layer 10 is preferably, for example, 1 nm or more and 20 nm or less.
[0055]
When the first magnetic layer 10 is a magnetization free layer, the second magnetic layer 20
may be a magnetization fixed layer or a magnetization free layer. When the second magnetic
layer 20 is a magnetization fixed layer, the magnetization direction of the second magnetic layer
20 does not substantially change even if strain is applied from the outside. Then, the electrical
resistance changes depending on the relative magnetization angle between the first magnetic
layer 10 and the second magnetic layer 20. The presence or absence of distortion is detected by
the difference in electrical resistance.
[0056]
When both the first magnetic layer 10 and the second magnetic layer 20 are magnetization free
layers, for example, the magnetostriction constant of the first magnetic layer 10 is set to be
different from the magnetostriction constant of the second magnetic layer 20. Ru.
[0057]
Whether the second magnetic layer 20 is a magnetization fixed layer or a magnetization free
layer, the thickness of the second magnetic layer 20 is preferably, for example, 1 nm or more and
20 nm or less.
[0058]
04-05-2019
17
For example, when the second magnetic layer 20 is a magnetization fixed layer, for example, a
synthetic AF structure using a laminated structure of diamagnetic layer / magnetic layer / Ru
layer / magnetic layer or the like may be used for the second magnetic layer 20. Can.
For example, IrMn is used for the diamagnetic layer.
In addition, as described later, a hard bias layer may be provided.
[0059]
In the strain sensing element 50, the spin of the magnetic layer is used. The area required for the
strain sensing element 50 is sufficient for a very small size. For example, when considering the
size of a square, the strain sensing element 50 may have a length of 10 nm × 10 nm to 20 nm
× 20 nm or more on one side.
[0060]
The area of the strain sensing element 50 is made sufficiently smaller than the area of the
transducing thin film 64 deflected by pressure. Here, the transducing thin film is a portion which
is surrounded by the fixed end as described above, is thinner than the fixed end at a certain
thickness, and is bent by an external pressure. Specifically, the area of the strain sensing element
50 is 1⁄5 or less of the area of the transducing thin film 64 in the substrate plane. In general, the
size of the transducing thin film 64 is about 60 μm or more and 600 μm or less as described
above. When the diameter of the transducing thin film 64 is as small as about 60 μm, the length
of one side of the strain sensing element 50 is, for example, 12 μm or less. When the diameter
of the transducing thin film is 600 μm, the length of one side of the strain sensing element 50 is
120 μm or less. This value is, for example, the upper limit of the size of the strain sensing
element 50.
[0061]
As compared with the value of the upper limit, the above-mentioned size of 10 nm or more and
04-05-2019
18
20 nm or less of one side is extremely small. For this reason, in consideration of the processing
accuracy of the element, the necessity of excessively reducing the size of the strain sensing
element 50 does not occur. Therefore, it is practically preferable that the size of one side of the
strain sensing element 50 be, for example, about 0.5 μm to 20 μm. If the element size becomes
extremely small, the magnitude of the demagnetizing field generated in the strain sensing
element 50 becomes large, which causes problems such as difficulty in bias control of the strain
sensing element 50. As the element size increases, the problem of the demagnetizing field does
not occur, which makes it easy to handle from an engineering point of view. From that point of
view, as described above, 0.5 μm or more and 20 μm or less is a preferable size.
[0062]
For example, the length of the strain sensing element 50 along the X-axis direction is 20 nm or
more and 10 μm or less. The length of the strain sensing element 50 in the X-axis direction is
preferably 200 nm or more and 5 μm or less.
[0063]
For example, the length of the strain sensing element 50 along the Y-axis direction
(perpendicular to the X-axis direction and parallel to the XY plane) is 20 nm or more and 10 μm
or less. The length of the strain sensing element 50 in the Y-axis direction is preferably 200 nm
or more and 5 μm or less.
[0064]
For example, the length along the Z-axis direction (direction perpendicular to the XY plane) of the
strain sensing element 50 is 20 nm or more and 100 nm or less.
[0065]
The length of the strain sensing element 50 in the X-axis direction may be the same as or
different from the length of the strain sensing element 50 in the Y-axis direction.
When the length of the strain sensing element 50 in the X-axis direction is different from the
04-05-2019
19
length of the strain sensing element 50 in the Y-axis direction, shape magnetic anisotropy occurs.
Thereby, the same function as the function obtained in the hard bias layer can be obtained.
[0066]
The direction of the current flowed in the strain sensing element 50 may be a direction from the
first magnetic layer 10 to the second magnetic layer 20 or may be a direction from the second
magnetic layer 20 to the first magnetic layer 10.
[0067]
FIG. 6B illustrates another configuration of a part of the pressure sensor according to the first
embodiment.
As shown in FIG. 6B, the strain sensing element 50 may include bias layers 55a and 55b (hard
bias layers). The bias layers 55a and 55b are provided to face the strain resistance change unit
50s.
[0068]
In this example, the second magnetic layer 20 is a magnetization fixed layer. The bias layers 55 a
and 55 b are juxtaposed to the second magnetic layer 20. The strain resistance change unit 50s
is disposed between the bias layers 55a and 55b. An insulating layer 54a is provided between the
bias layer 55a and the strain resistance change unit 50s. An insulating layer 54b is provided
between the bias layer 55b and the strain resistance change unit 50s.
[0069]
The bias layers 55 a and 55 b apply a bias magnetic field to the first magnetic layer 10. As a
result, the magnetization direction of the first magnetic layer 10 can be biased to a proper
position, and can be made into a single magnetic domain.
[0070]
04-05-2019
20
The size of each of the bias layers 55a and 55b (in this example, the length along the Y-axis
direction) is, for example, 100 nm or more and 10 μm or less.
[0071]
The size of each of the insulating layers 54a and 54b (in this example, the length along the Y-axis
direction) is, for example, 1 nm or more and 5 nm or less.
[0072]
Next, an example of the operation of the present embodiment will be described.
FIG. 7A and FIG. 7B are schematic views illustrating the operation of the pressure sensor
according to the first embodiment.
FIG. 7A is a schematic cross-sectional view when cut along the straight line 64d of FIG. FIG. 7B is
a schematic view illustrating the operation of the pressure sensor. FIGS. 8A and 8B are schematic
views illustrating the relationship between the position on the film surface of the transducing
thin film and the strain. FIG. 8A is a schematic plan view illustrating the film surface of the
transducing thin film. FIG. 8B is a graph illustrating the relationship between the position on the
film surface of the transducing thin film and the strain. The horizontal axis of the graph shown in
FIG. 8 (b) represents the distance from the center of gravity 64b. The vertical axis of the graph
shown in FIG. 8 (b) represents distortion. FIG. 9A and FIG. 9B are schematic views illustrating the
relationship between the position on the film surface of another transducing thin film and the
strain. FIG. 9A is a schematic plan view illustrating the film surface of another transducing thin
film. FIG. 9B is a graph illustrating the relationship between the position on the film surface of
another transducing thin film and the strain. The horizontal axis of the graph shown in FIG. 9 (b)
represents the distance from the center of gravity 64b. The vertical axis of the graph shown in
FIG. 9 (b) represents distortion. FIG. 10 is a graph illustrating the optimum strain range of the
strain sensing element. The horizontal axis of the graph shown in FIG. 10 represents the distance
from the center of gravity 64 b. The vertical axis of the graph shown in FIG. 10 represents
distortion.
[0073]
04-05-2019
21
As shown in FIG. 7A, in the pressure sensor 310 according to the present embodiment, the
transducing thin film 64 is bent by receiving a stress 80 from a medium such as air. For example,
stress 81 (for example, a tensile stress) is applied to the transducing thin film 64 by bending the
transducing thin film 64 so that the film surface 64 a is convex. At this time, a stress 81 is also
applied to the strain sensing element 50 provided on the film surface 64 a of the transducing
thin film 64 to cause strain. Thereby, in the strain sensing element 50, the electrical resistance
between one end and the other end of the strain sensing element 50 changes according to the
change in strain due to the inverse magnetostrictive effect. When the transducing thin film 64
bends so that the film surface 64 a is concaved, compressive stress is applied to the transducing
thin film 64.
[0074]
As shown in FIG. 7B, signals 50sg corresponding to the above-described stress can be obtained
from each of the plurality of strain sensing elements 50. For example, the first signal sg1 is
obtained from the first strain sensing element 50A. A second signal sg2 is obtained from the
second strain sensing element 50B. A third signal sg3 is obtained from the third strain sensing
element 50C. A fourth signal sg4 is obtained from the fourth strain sensing element 50D. The
plurality of signals 50 sg are processed by the processing circuit 113.
[0075]
Here, as shown in FIGS. 8A and 8B, when the shape of the film surface 64a of the transducing
thin film 64 is circular, the center of gravity 64b of the film surface 64a of the transducing thin
film 64 is used. The distortion of the film surface 64a increases as the distance r of the distance.
The distortion of the film surface 64a is maximized at a position slightly inside the fixed end of
the transducing thin film 64 (the position where the distance from the center of gravity 64b is
r0) (the position where the distance from the center of gravity 64b is r1). Alternatively, as shown
in FIGS. 9A and 9B, even when the shape of the film surface 64a of the transducing thin film 64
is rectangular (here, a square is included), the film of the transducing thin film 64 is used. As the
distance y from the center of gravity 64b of the surface 64a increases, distortion of the film
surface 64a increases. The distortion of the film surface 64a is maximized at a position slightly
inside the fixed end of the transducing thin film 64 (the distance from the center of gravity 64b
is y0) (the distance from the center of gravity 64b is y1).
[0076]
04-05-2019
22
The fixed end of the transducing thin film 64 (the position where the distance from the center of
gravity 64b is r0) is fixed to the non-hollow portion 71 (base 71a) at the edge 64eg. Therefore,
the distortion at the fixed end of the transducing thin film 64 is smaller than the distortion at a
position slightly inside the fixed end (the position where the distance from the center of gravity
64 b is y1).
[0077]
As shown in FIG. 10, the strain sensing element 50 has an optimum strain range A1. The strain
sensing element 50 can not detect strain of the film surface 64a smaller than the optimal strain
range A1. With regard to the strain of the film surface 64a larger than the optimum strain range
A1, the stress 81 applied to the strain sensing element 50 becomes excessive, and the strain
generated in the strain sensing element 50 becomes excessive. Therefore, the strain sensing
element 50 can not accurately sense the strain of the film surface 64a larger than the optimum
strain range A1. When the gauge factor (GF) of the strain sensing element 50 is relatively high,
the optimum strain range A1 is relatively narrow. The gauge factor of the strain sensing element
50 is the amount of change in electrical resistance (dR / R) per unit strain (dε).
[0078]
Therefore, for example, when the pressure sensor 310 acquires a pressure due to a loud sound
(sound wave) (for example, a sound of about 140 dBspl or more), the first strain arranged at the
farthest position from the center of gravity 64b among the plurality of strain sensing elements
50 The stress 81 applied to the sensing element 50A may be excessive, and the strain generated
in the first strain sensing element 50A may be excessive. Then, the first strain sensing element
50A can not accurately sense the strain of the film surface 64a, and transmits the saturated first
signal sg1 to the processing circuit 113.
[0079]
On the other hand, in the pressure sensor 310 according to the embodiment, when the first
signal sg1 of the first strain sensing element 50A is larger than the first threshold (for example,
the upper limit value of the optimum strain range A1), the processing circuit 113 The switching
process is performed between the first strain sensing element 50A and the second strain sensing
element 50B, and the second signal sg2 of the second strain sensing element 50B is output.
04-05-2019
23
[0080]
On the other hand, for example, when the pressure sensor 310 acquires a pressure by a small
volume sound (sound wave), the first strain sensing element 50A disposed at a position farthest
from the center of gravity 64b among the plurality of strain sensing elements 50 As compared
with the two-strain sensing element 50B, a large stress 81 is applied to cause a large strain.
Therefore, the first strain sensing element 50A senses strain of the film surface 64a with higher
sensitivity, and transmits the first signal sg1 to the processing circuit 113. The processing circuit
113 outputs the first signal sg1 of the first strain sensing element 50A when the first signal sg1
of the first strain sensing element 50A is within the optimum strain range A1.
[0081]
Thus, the processing circuit 113 generates the first signal sg1 obtained from the first strain
sensing element 50A when an external pressure is applied to the film surface 64a of the
transducing thin film 64 and the film surface 64a of the transducing thin film 64. One of the
second signals sg2 obtained from the second strain sensing element 50B when an external
pressure is applied is output as an output signal. As a result, the pressure sensor 310 according
to the embodiment can sensitively detect a wide range of pressure ranging from low volume to
high volume, for example. Therefore, the pressure sensor 310 with a wide dynamic range can be
realized.
[0082]
When an external pressure is applied to the film surface 64 a of the transducing thin film 64, the
film surface 64 a of the transducing thin film 64 moves. The strain on the film surface 64a of the
transducing thin film 64 at that time differs depending on the position on the film surface 64a as
described above. On the other hand, the signal-to-noise ratio (SNR: Signal-to-Noise Ratio) of the
pressure sensor 310 is increased by using a plurality of (N) strain sensing elements instead of a
single strain sensing element 50. The SNR improvement is expressed by the following equation.
SNR = SNR single element + 20 × log ((N) (1)
04-05-2019
24
[0083]
Here, the plurality of strain sensing elements 50 are electrically connected in series or in parallel.
When a plurality of strain sensing elements 50 can be disposed on the transducing thin film 64
as in the equation (1), using a plurality of strain sensing elements 50 is more advantageous for
improving SNR. However, in the case of a spin MEMS sensor, since an MR element is used, the
anisotropy of strain is one of the important factors. If the strain sensing element 50 is not
arranged in a region where the direction of the anisotropic strain applied to each of the plurality
of strain sensing elements 50 is the same, the rise effect by the plurality of strain sensing
elements 50 can not be obtained.
[0084]
On the other hand, in the present embodiment, it is one of the necessary conditions that the
strain sensing element 50 is disposed at a place where the magnitude of strain is different when
the same pressure is applied. Therefore, the following more preferable embodiment is provided
as the arrangement of the strain sensing element 50 compatible with the SNR improvement by
the plurality of strain sensing elements 50 as described above.
[0085]
FIG. 11A and FIG. 11B are schematic plan views showing an example of the pressure sensor
according to the present embodiment. FIG. 12A to FIG. 12C are schematic views showing an
example of connection of sensor lines according to the present embodiment. FIG. 11A is a
schematic plan view showing an example in which the shape of the film surface of the
transducing thin film is circular. FIG. 11 (b) is a schematic plan view showing an example in
which the shape of the film surface of the transducing thin film is rectangular.
[0086]
In the example shown in FIG. 11A and FIG. 11B, the magnitudes of distortion are different at two
levels. Further, a plurality of strain sensing elements 50 are disposed on the film surface 64 a of
the transducing thin film 64. In the example shown to Fig.11 (a), four sensor lines are provided
04-05-2019
25
as a sensor line electrically connected in series. Fifteen strain sensing elements 50 are connected
in series to the first A line LA1 (first line), and are arranged near the circumferential fixed end so
as to maximize the strain. Similarly, 15 strain sensing elements 50 are also disposed in the
second A line LA2 (second line) as an arrangement in which the distortion is maximized. These
are symmetrical positions at which the vectors of the x-y anisotropic strain become substantially
similar when the transducing thin film 64 is deformed. Assuming that the position of 12 o'clock
is 0 degrees on the clock and the position of 6 o'clock is 180 degrees, the magnetization fixing
direction of the strain detection element 50 is set so that the strain detection element 50 reacts
near 0 or 180 degrees. The case is assumed.
[0087]
As shown in FIG. 12A, the first A line LA1 and the second A line LA2 may be connected in series
with each other for SNR improvement. Alternatively, as shown in FIG. 12B, the first A line LA1
and the second A line LA2 may be connected in parallel with each other. Alternatively, as shown
in FIG. 12C, the first A line LA1 and the second A line LA2 may be respectively used to form a
bridge circuit.
[0088]
On the other hand, the first B line LB1 (third line) and the second B line LB2 (fourth line) are both
arranged at a position r closer to the center of gravity. In this case, the distortion when the same
pressure as that described above is applied is smaller than that of the A line (the first A line LA1
and the second A line LA2: the first strain sensing element group). Therefore, B line (D line) is
placed at a position where the amount of distortion is reduced when detecting a large volume or
when shipping as a product with the same SNR as other pressure sensors, with high sensitivity
due to variations in transducing thin film 64. This example is effective when the signals of the
sensors of the first B line BL1 and the second B line BL2 (second strain sensing element group)
are used as output signals. In the B line as well as in the A line, as shown in FIG. 12A, the first B
line BL1 and the second B line LB2 may be electrically in series with each other. Alternatively, as
shown in FIG. 12B, the first B line BL1 and the second B line BL2 may be connected in parallel
with each other. Alternatively, as shown in FIG. 12C, the first B line BL1 and the second B line
BL2 may form a bridge circuit.
[0089]
04-05-2019
26
In the example shown in FIG. 11B, the shape of the film surface 64a of the transducing thin film
64 is rectangular. Therefore, the region where the x-y anisotropic strain can be obtained can be
wider than the circular film surface 64a. Even in the case of the rectangular film surface 64a, the
strain at the time of pressure application becomes large in the area near the fixed end, so the
output of the A-line sensor is greater than the output of the B-line sensor at small pressure
application when the output is not saturated. Also, the output of the B-line sensor is smaller than
the output of the A-line sensor. As in the case of the circular film surface 64a, the B-line is
disposed farther from the center of gravity than the A-line. As in the case of the circular film
surface 64a, the first A-line LA1 and the second A-line LA2 may be connected in series with each
other for SNR improvement (see FIG. 12A). Alternatively, the first A line LA1 and the second A
line LA2 may be connected in parallel with each other (see FIG. 12 (b)). Alternatively, the first A
line LA1 and the second A line LA2 may be respectively used to form a bridge circuit (see FIG. 12
(c)).
[0090]
On the other hand, the B lines are both arranged at a position r closer to the center of gravity. In
this case, the distortion when the same pressure as that in the above case is applied is smaller
than in the case of the A line. Therefore, when detecting a larger volume, or when the product
becomes highly sensitive due to the variation of the transducing thin film 64 and shipped as a
product with the same SNR as other pressure sensors, the B line placed at a position where the
distortion amount is reduced This example is effective when using a sensor signal as an output
signal. Also in the B line, as in the A line, the first B line BL1 and the second B line LB2 may be
electrically connected to each other in series (see FIG. 12A). Alternatively, the first B line BL1 and
the second B line LB2 may be connected in parallel with each other (see FIG. 12B). Alternatively,
the first B line LB1 and the second B line LB2 may form a bridge circuit (see FIG. 12C).
[0091]
FIG. 13A and FIG. 13B are schematic plan views showing an example of the pressure sensor
according to the present embodiment. FIG. 13A is a schematic plan view showing an example in
which the shape of the film surface of the transducing thin film is circular. FIG. 13 (b) is a
schematic plan view showing an example in which the shape of the film surface of the
transducing thin film is rectangular.
04-05-2019
27
[0092]
In each of the examples shown in FIGS. 13A and 13B, not only two of the A line and the B line,
but two of the A line, the B line, and the C line are strain sensing elements 50 disposed at
different positions. It shows the case where there are three lines of line.
[0093]
The method of use is similar to the example described above with respect to FIGS. 11 (a) -12 (c).
FIGS. 11A and 11B show an example in which the lines of the plurality of strain sensing elements
50 connected in series with each other at different distances from the center of gravity are two
lines. FIGS. 13A and 13B show three lines in which the lines of the plurality of strain sensing
elements 50 connected in series are connected at different distances from the center of gravity.
The number of lines is not limited to two and three, but may be four and five, etc. There may be
two or more lines of sensors.
[0094]
FIGS. 14 (a) and 14 (b) are schematic diagrams showing the circuit after the output of the line.
FIGS. 15 (a) and 15 (b) are flowcharts illustrating a method of generating a control signal. FIG.
14A and FIG. 15A show an example of two lines. FIGS. 14 (b) and 15 (b) show examples of three
lines.
[0095]
The line of the output signal LASg from the A line and the line of the output signal LBSg from the
B line are connected to the multiplexer 81. The multiplexer 81 is a circuit that selects and
outputs one line for input signals from a plurality of lines. A line of a control signal CSg for
determining which line to output is connected to the multiplexer 81. In the example shown in
FIG. 14A, based on the control signal CSg, the multiplexer 81 uses either the output signal LASg
of the A line or the output signal LBSg of the B line as an output signal in real time during
measurement. . In the example shown in FIG. 14B, the multiplexer 81 selects any of the output
signal LASg of the A line, the output signal LBSg of the B line, and the output signal LCSg of the C
line in real time during measurement based on the control signal CSg. Let one be the output
04-05-2019
28
signal. The control signal CSg may be generated based on the output signal LASg from the A line
and the output signal LBSg from the B line as to which line the signal is to be used as the output
signal, or another sensor for control judgment. May be disposed on the transducing thin film, and
the control signal CSg may be generated based on the signal.
[0096]
An example of the case of generating the control signal CSg based on the output signal LASg
from the A line and the output signal LBSg from the B line will be described with reference to
FIG. It is determined whether the output signal LASg from the A line exceeds a preset saturation
threshold (first threshold) (step S51). When the output signal LASg of the A line does not exceed
the first threshold (step S51: No), the control signal CSg for selecting the A line is generated (step
S52). If the output signal LASg of the A line exceeds the first threshold (step S51: Yes), a large
undetectable pressure is applied to the A line, and the control signal CSg for selecting the B line
is generated. (Step S53).
[0097]
It shows about the case where C line is further provided, referring FIG.15 (b). The output signal
LASg of the A-line is measured, and it is determined whether it exceeds the threshold (first
threshold) of the A-line set in advance (step S61). If the output signal LASg of the A line does not
exceed the first threshold (step S61: No), the control signal CSg for selecting the A line is
generated (step S62). When the output signal LASg of the A line exceeds the first threshold (step
S61: Yes), the output signal LBSg of the B line is measured, and it is set to the threshold (second
threshold) of the B line set in advance. It is determined whether it exceeds (step S63). If the
output signal LBSg of the B line does not exceed the second threshold (step S63: No), the control
signal CSg for selecting the B line is generated (step S64). When the output signal LBSg of the B
line exceeds the second threshold (step S63: Yes), a large undetectable pressure is applied to
both the A line and the B line, so the control signal to select the C line CSg is generated (step
S65).
[0098]
In order to make such control determination in real time at the time of measurement, the clock
frequency of the processor generating the control signal CSg needs to be sufficiently faster than
04-05-2019
29
the fluctuation of the object to be measured. For pressure measurement that does not fluctuate at
high speed such as atmospheric pressure, it is originally sufficient, and even in the audible range
of sounds, even high frequencies up to 20 kHz, and even tens of to hundreds of kHz for
ultrasonic measurement In the case of targeting the degree, it can be sufficiently coped with. The
clock frequency of the processor for generating the control signal CSg needs to be at least 100
times, preferably 1000 times higher than the frequency to be measured as described above, but
in the audible range up to 20 kHz. The clock frequency of 2 megahertz (MHz) to 20 MHz is
sufficient, and for ultrasonic waves of about 100 kHz, the clock frequency of about 10 MHz to
100 MHz is sufficient, and it is necessary to be several tens to several hundreds of MHz It is.
When ultrasonic waves of 1 MHz are to be measured, a clock frequency of 100 MHz to 1 GHz is
sufficient. In any case, although the cost varies depending on the clock frequency, it is a value
that can be sufficiently realized as the processor clock frequency, and real-time selection control
judgment can be made while performing measurement.
[0099]
An example of the operation of this embodiment will be further described with reference to the
drawings. 16 (a) and 16 (b) are flowcharts illustrating the operation of the pressure sensor
according to the first embodiment.
[0100]
As shown in FIG. 16A, in the case where the pressure sensor 310 includes the first strain sensing
element 50A and the second strain sensing element 50B, the processing circuit 113 is configured
to receive the first strain sensing element 50A from the first strain sensing element 50A. The
signal sg1 is received (acquired), and the second signal sg2 is received from the second strain
sensing element 50B (step S11).
[0101]
Subsequently, the processing circuit 113 determines whether the first signal sg1 of the first
strain sensing element 50A is larger than a first threshold (for example, the upper limit value of
the optimum strain range A1) (step S12).
When the first signal sg1 of the first strain sensing element 50A is not larger than the first
threshold (step S12: No), the processing circuit 113 selects (outputs) the first signal sg1 of the
04-05-2019
30
first strain sensing element 50A. (Step S14). On the other hand, when the first signal sg1 of the
first strain sensing element 50A is larger than the first threshold (step S12: Yes), the processing
circuit 113 combines the first strain sensing element 50A and the second strain sensing element
50B with each other. The switching process is performed during the period of time to select
(output) the second signal sg2 of the second strain sensing element 50B (step S13).
[0102]
Subsequently, the processing circuit 113 receives the first signal sg1 from the first strain sensing
element 50A, receives the second signal sg2 from the second strain sensing element 50B, and
repeats the above-described operation in steps S11 to S14 ( Steps S11 to S14).
[0103]
As shown in FIG. 16B, when the pressure sensor 310 includes the first strain sensing element
50A, the second strain sensing element 50B, the third strain sensing element 50C, and the fourth
strain sensing element 50D, The processing circuit 113 receives the first signal sg1 from the first
strain sensing element 50A, receives the second signal sg2 from the second strain sensing
element 50B, and receives the third signal sg3 from the third strain sensing element 50C, The
fourth signal sg4 is received from the fourth strain sensing element 50D (step S21).
[0104]
Subsequently, the processing circuit 113 determines whether the first signal sg1 of the first
strain sensing element 50A is larger than a first threshold (for example, the upper limit value of
the optimum strain range A1) (step S22).
When the first signal sg1 of the first strain sensing element 50A is not larger than the first
threshold (step S22: No), the processing circuit 113 selects (outputs) the first signal sg1 of the
first strain sensing element 50A. (Step S23).
On the other hand, when the first signal sg1 of the first strain sensing element 50A is larger than
the first threshold (step S22: Yes), the processing circuit 113 combines the first strain sensing
element 50A and the second strain sensing element 50B with each other. In the meantime, the
switching process is performed to determine whether the second signal sg2 of the second strain
sensing element 50B is larger than the second threshold (for example, the upper limit value of
the optimum strain range A1) (step S24).
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[0105]
When the second signal sg2 of the second strain sensing element 50A is not larger than the
second threshold (step S24: No), the processing circuit 113 selects (outputs) the second signal
sg2 of the second strain sensing element 50B. (Step S25). On the other hand, when the second
signal sg2 of the second strain sensing element 50B is larger than the second threshold (step
S24: Yes), the processing circuit 113 combines the second strain sensing element 50B and the
third strain sensing element 50C. In the meantime, the switching process is performed to
determine whether the third signal sg3 of the third strain sensing element 50C is larger than the
third threshold (for example, the upper limit value of the optimum strain range A1) (step S26).
[0106]
If the third signal sg3 of the third strain sensing element 50C is not larger than the third
threshold (step S26: No), the processing circuit 113 selects the third signal sg3 of the third strain
sensing element 50C (output) (Step S28). On the other hand, when the third signal sg3 of the
third strain sensing element 50C is larger than the third threshold (step S26: Yes), the processing
circuit 113 combines the third strain sensing element 50C and the fourth strain sensing element
50D. The switching process is performed during the period of time to select (output) the fourth
signal sg4 of the fourth strain sensing element 50D (step S27).
[0107]
Subsequently, the processing circuit 113 receives the first signal sg1 from the first strain sensing
element 50A, receives the second signal sg2 from the second strain sensing element 50B, and
receives the third signal sg3 from the third strain sensing element 50C. Then, the fourth signal
sg4 is received from the fourth strain sensing element 50D, and the operation described above
with respect to steps S21 to S28 is repeated (step S21 to step S28).
[0108]
Thus, the pressure sensor 310 according to the embodiment can detect the pressure in a wider
range with high sensitivity.
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Therefore, the pressure sensor 310 with a wider dynamic range can be realized. Further, the
processing circuit 113 can execute dynamic switching processing in order to repeat the
operation, and can respond relatively quickly to, for example, a wide range of pressure ranging
from small volume to large volume.
[0109]
In the pressure sensor 310 according to the embodiment, the switching clock of the processing
circuit 113 needs to be sufficiently higher than the frequency of the detected pressure (for
example, the pressure by the detected sound). On the other hand, the frequency of the audible
sound is, for example, about 10 kilohertz (kHz) or less. The clock frequency of the processing
circuit 113 is, for example, on the order of about gigahertz (GHz). The clock frequency of the
processing circuit 113 is about five digits higher than the frequency of the audible sound.
Therefore, the pressure sensor 310 according to the embodiment can detect pressure in a wide
frequency band with high sensitivity.
[0110]
Second Embodiment FIG. 17 is a schematic plan view illustrating the configuration of another
pressure sensor according to a second embodiment. As illustrated in FIG. 17, in the pressure
sensor 330, the plurality of strain sensing elements 50 are arranged at substantially equal
intervals along the straight line 64c and the straight line 64d. For example, four strain sensing
elements 50 are disposed on each side of the center (corresponding to the center of gravity 64b)
in the straight line 64c. The strain sensing elements 50 are arranged four by four on both sides
of the center (corresponding to the center of gravity 64 b) of the straight line 64 d. In this
example, the strain sensing element 50 is disposed at a substantially symmetrical position with
respect to the center of gravity 64 b.
[0111]
That is, also in the pressure sensor 330 according to the present embodiment, a plurality of
strain sensing elements 50 are provided. For example, the sensor unit 72 (first sensor unit 72A)
includes a first strain sensing element 50A, a second strain sensing element 50B, a third strain
sensing element 50C, and a fourth strain sensing element 50.
04-05-2019
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[0112]
For example, the first strain sensing element 50A is a strain sensing element 50a, the second
strain sensing element 50B is a strain sensing element 50b, the third strain sensing element 50C
is a strain sensing element 50c, and the fourth strain sensing element 50D is strain sensing The
element 50d is used. A first strain sensing element 50A (strain sensing element 50a), a second
strain sensing element 50B (strain sensing element 50c), a third strain sensing element 50C
(strain sensing element 50c), and a fourth strain sensing element 50D (strain A straight line
(straight line 64d and straight line 64c) connecting the detection element 50d) passes through
the center of gravity 64b.
[0113]
In the pressure sensor 330, the fixing portions 67a and 67c are disposed at the intersections of
the straight line 64c and the edge 64eg of the transducing thin film 64. The fixing portion 67 b
and the fixing portion 67 d are disposed at the intersection of the straight line 64 d and the edge
64 eg of the transducing thin film 64.
[0114]
The fourth strain sensing element 50D, the third strain sensing element 50C, the second strain
sensing element 50B, and the first strain sensing element 50A are arranged in this order along
the straight line 64d from the center of gravity 64b to the fixing portion 67d. line up. The fourth
strain sensing element 50D, the third strain sensing element 50C, the second strain sensing
element 50B, and the first strain sensing element 50A are arranged in this order along the
straight line 64d from the center of gravity 64b to the fixing portion 67b. line up. The fourth
strain sensing element 50D, the third strain sensing element 50C, the second strain sensing
element 50B, and the first strain sensing element 50A are arranged in this order along the
straight line 64c from the center of gravity 64b to the fixing portion 67a. line up. The fourth
strain sensing element 50D, the third strain sensing element 50C, the second strain sensing
element 50B, and the first strain sensing element 50A are arranged in this order along the
straight line 64c from the center of gravity 64b to the fixing portion 67c. line up.
04-05-2019
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[0115]
For example, the first strain sensing element 50A is a strain sensing element 50a, and the second
strain sensing element 50B is a strain sensing element 50c. A straight line (straight line 64d and
straight line 64c) connecting the first strain sensing element 50A (strain sensing element 50a)
and the second strain sensing element 50B (strain sensing element 50c) passes through the
center of gravity 64b.
[0116]
The pressure sensor 330 according to the embodiment can detect the pressure in a wide range,
for example, from a small volume to a large volume with high sensitivity by performing the
operations described above with reference to FIGS. 7A to 16B. Therefore, the pressure sensor
310 with a wide dynamic range can be realized. The pressure sensor 330 according to the
embodiment can detect pressure in a wide frequency band with high sensitivity.
[0117]
FIG. 18 is a schematic plan view illustrating the configuration of another pressure sensor
according to the second embodiment. As shown in FIG. 18, in the pressure sensor 331 according
to the present embodiment, the shape of the fixing portion 67 is a ring shape. The fixing portion
67 is along the edge 64eg of the transducing thin film 64. The fixing portion 67 fixes the edge
64eg of the transducing thin film 64 continuously. Since the edge 64eg of the transducing thin
film 64 is continuously fixed, the deflection amount of the transducing thin film 64 can be made
to depend on the distance from the center of gravity 64b.
[0118]
FIG. 19 is a schematic plan view illustrating the configuration of another pressure sensor
according to the second embodiment. As shown in FIG. 19, in another pressure sensor 332
according to the present embodiment, the plurality of strain sensing elements 50 are arranged
substantially at equal intervals along the straight line 64 c and the straight line 64 d. Four strain
sensing elements 50 are disposed on both sides of the center of gravity 64b of the straight line
64c, and four strain sensing elements 50 are disposed on both sides of the center of gravity 64b
04-05-2019
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of the straight line 64d.
[0119]
Each of the pressure sensor 331 and the pressure sensor 332 performs, for example, high
sensitivity detection of a wide range of pressure ranging from small volume to large volume by
performing the operation described above with reference to FIGS. 7A to 16B. it can. Therefore,
the pressure sensor 310 with a wide dynamic range can be realized. Each of the pressure sensor
331 and the pressure sensor 332 can detect pressure in a wide frequency band with high
sensitivity.
[0120]
Third Embodiment The present embodiment relates to a method of manufacturing a pressure
sensor (for example, a pressure sensor according to the first embodiment). FIG. 20 is a flowchart
illustrating the method for manufacturing the pressure sensor according to the third
embodiment. FIG. 21A to FIG. 21D are schematic perspective views in order of the processes,
illustrating the method for manufacturing the pressure sensor according to the third
embodiment. FIG. 22 is a schematic view illustrating the confirmation step in the method of
manufacturing a pressure sensor according to the third embodiment. The horizontal axis of the
graph shown in FIG. 22 (a) represents the distance from the center of gravity 64b. The vertical
axis of the graph shown in FIG. 22A represents distortion. These figures are examples of a
method of manufacturing the pressure sensor 310. In FIG. 21A to FIG. 21D, the shapes and sizes
of the respective elements are appropriately changed from FIG. FIG. 22A is a graph illustrating
the optimum strain range of the strain sensing element. FIG. 22B is a schematic view illustrating
the operation of the pressure sensor in the confirmation step.
[0121]
As shown in FIG. 20, a transducing film is formed (step S101). For example, as shown in FIG.
21A, the transducing film 64fm to be the transducing thin film 64 is formed on the substrate
70s. For example, a silicon substrate is used as the substrate 70s. For example, a silicon oxide
film is used for the transducing film 64fm. For example, as in a pressure sensor 330 (see FIG. 17)
according to the second embodiment, a fixing portion 67 (for example, fixing portions 67a to
67d) for intermittently holding the edge 64eg of the transducing thin film 64 is formed. In this
04-05-2019
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step, the transducing film 64fm may be processed to form a portion to be the fixing portion 67.
[0122]
As shown in FIG. 20, the first conductive layer is formed (step S102). For example, as shown in
FIG. 21B, a conductive film is formed on the transducing film 64fm (or the transducing thin film
64), and the conductive film is processed into a predetermined shape to form a first conductive
layer. (Conductive layer 61f) is formed. This conductive layer can be, for example, at least a part
of the first wiring 57.
[0123]
As shown in FIG. 20, the strain sensing element 50 is formed (step S103). For example, as shown
in FIG. 21C, a laminated film to be the strain sensing element 50 is formed on a part of the
conductive layer 61f. The laminated film is formed, for example, of a buffer layer, a seed layer, an
antiferromagnetic layer, a magnetic layer, a magnetic coupling layer, a magnetic layer, an
intermediate layer, a magnetic layer, a high magnetostrictive film, a cap film, etc. including. The
laminated film is processed into a predetermined shape to form a strain sensing element 50 (for
example, strain sensing elements 50a to 50d).
[0124]
As shown in FIG. 20, the second conductive layer is formed (step S104). For example, as shown in
FIG. 21D, an insulating film (not shown) is formed so as to cover the strain sensing element 50,
and a part of the insulating film is removed to expose the upper surface of the strain sensing
element 50. A conductive film is formed thereon and processed into a predetermined shape to
obtain a second conductive layer (conductive layer 62f).
[0125]
As shown in FIG. 20, the wiring (for example, the first wiring 57) connected to the first
conductive layer and the wiring (for example, the second wiring 58) connected to the second
conductive layer are formed (step S105) . A wiring may be formed by at least one of the
04-05-2019
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formation of the first conductive layer and the formation of the second conductive layer. That is,
at least a part of the process for processing the wiring may be performed simultaneously with at
least a part of the formation of the first conductive layer, the formation of the second conductive
layer and the formation of the strain sensing element. That is, at least a part of steps S102 to
S105 may be performed simultaneously as long as technically possible, and the order may be
changed.
[0126]
As shown in FIG. 20, etching is performed from the back surface (lower surface) of the substrate
70s (step S106). For example, Deep-RIE or the like is used for this processing. At this time, the
Bosch process may be performed. As a result, as shown in FIG. 21D, the cavity 70 is formed in
the substrate 70s. The portion where the cavity 70 is not formed is the non-cavity 71. Thereby,
the transducing thin film 64 is formed.
[0127]
In the case of forming the fixing portion 67 (for example, the pressure sensor 331 etc.) for
continuously holding the edge 64eg of the transducing thin film 64, the etching from the back
surface of the substrate 70s is performed simultaneously with the transducing thin film 64 at the
same time. The fixing portion 67 is formed.
[0128]
As described above, in this manufacturing method, a film to be the transducing thin film 64
(transducing film 64 fm) is formed on a semiconductor substrate, and a film to be the strain
sensing element 50 (strain resistance change portion) is formed thereon. And patterned in the
shape of the element.
According to the present embodiment in which the element is formed and it is possible to
conduct electricity, the transducing film 64 fm is etched from the back surface of the substrate to
form the transducing thin film 64, whereby a highly sensitive pressure sensor can be
manufactured.
[0129]
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Here, variations may occur in the structure of the transducing thin film 64 manufactured by the
manufacturing method described above with reference to steps S101 to S106. This may cause
variations in the performance of the transducing thin film 64 (e.g., SNR (signal-noise ratio)). As
the “variation” in this example, for example, the dispersion between production lots and the
like can be mentioned.
[0130]
On the other hand, in the method of manufacturing a pressure sensor according to the
embodiment, a confirmation test of the first strain sensing element 50A and the second strain
sensing element 50B is performed (step S107). More specifically, as shown in FIGS. 22A and 22B,
the first signal sg1 transmitted from the first strain sensing element 50A to the processing circuit
113 has a first threshold (for example, an optimum strain). It is checked whether it is larger than
the upper limit value of the range A1. If the first signal sg1 of the first strain sensing element
50A is not larger than the first threshold, the first strain sensing element 50A is selected and
fixed (step S108). At this time, the step of blocking the second signal sg2 transmitted from the
second strain sensing element 50B to the processing circuit 113 is performed. For example, a
wire connecting the second strain sensing element 50B and the processing circuit 113 is
disconnected (step S108).
[0131]
On the other hand, when the first signal sg1 of the first strain sensing element 50A is larger than
the first threshold, the second strain sensing element 50B is selected and fixed (step S108). At
this time, the step of blocking the first signal sg1 transmitted from the first strain sensing
element 50A to the processing circuit 113 is performed. For example, the wiring connecting the
first strain sensing element 50A and the processing circuit 113 is disconnected (step S108).
Although two strain sensing elements 50 are described in FIGS. 22A and 22B, a confirmation test
of three or more strain sensing elements 50 may be performed.
[0132]
According to the method of manufacturing the pressure sensor according to the embodiment,
even when the performance of the transducing thin film 64 varies, it is possible to cope more
flexibly by adopting the applicable strain sensing element 50. Manufacturing efficiency can be
04-05-2019
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improved.
[0133]
An example of absorbing variations in the manufacture of the transducing thin film 64 will be
further described with reference to the drawings.
FIGS. 23 (a) and 23 (b) are schematic diagrams showing an example in which one of a plurality of
lines is fixed and output. FIG. 23A shows an example of two lines. FIG. 23 (b) shows an example
of three lines.
[0134]
In the examples of FIGS. 23A and 23B, instead of switching and outputting the output signal
LASg from the A line and the output signal LBSg from the B line in real time, one of the lines is
fixedly output. As such, an electrical circuit is formed. When the sensitivity of the transducing
thin film 64 is good or bad, and there are manufacturing variations, the pressure variations with
the manufacturing variations are not shipped as pressure sensors with different SNRs or acoustic
microphones, but either the A line or B line is used as the final output. It will be judged by the
pre-shipment inspection about whether to do it. Then, by setting only one line to be an output
signal, variation in SNR at the time of product shipment is suppressed.
[0135]
Although not shown, after the sensor device is completed, measurement of the output signal
LASg from the A line and measurement of the output signal LBSg from the B line are performed.
From the measurement result, it is determined which signal of the line is selected as the final
output and the product is shipped. Based on the judgment result, any one of the output signal
LASg of the A line and the output signal LBSg of the B line is electrically cut off so as not to be
finally output, and then shipped as a product. This electrical shutoff means physically
disconnects the wiring (makes a high resistance state or a scratch, if there is a method of
selecting either the A line or the B line using a selection switch (electric switch). It does not
matter which method is used, such as adding and insulating.
04-05-2019
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[0136]
FIG. 23A shows an example in the case of two lines of A line and B line. As in FIG. 23 (b), the
same applies to the cases of the A line, the B line, the C line and three lines, or four or more lines
not shown.
[0137]
In this way, while pressure and sound can not be acquired in a wide dynamic range as in the
example described above with reference to FIG. 14, even if there are manufacturing variations of
the transducing thin film 64, such variations are dragged. Instead, the final output as a product
can be shipped as a product with uniform sensitivity and SNR.
[0138]
This is because, in the case of an acoustic sensor (microphone) application, when used as a single
microphone, the variation of each sensor does not matter so much.
On the other hand, it may be important in applications (sound processing systems) where noise
cancellation is performed using a plurality of microphones, speech recognition is performed, and
machine failure or abnormality determination is performed. In this case, it may be more
important that there are multiple microphones with uniform performance, rather than a mixture
of multiple single microphones with high performance and standard performance microphones.
[0139]
Fourth Embodiment FIG. 24 is a schematic perspective view illustrating a pressure sensor
according to a fourth embodiment. As shown in FIG. 24, in the pressure sensor 360 according to
the present embodiment, a semiconductor circuit unit 110 is provided in addition to the base 71
a and the sensor unit 72 (first sensor unit 72A). A base 71 a is provided on the semiconductor
circuit unit 110, and a sensor unit 72 is provided on the base 71 a.
[0140]
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41
The semiconductor circuit unit 110 includes, for example, a semiconductor substrate 111 and a
transistor 112.
[0141]
The semiconductor substrate 111 includes the main surface 111 a of the semiconductor
substrate 111.
The semiconductor substrate 111 includes an element region 111 b provided on the major
surface 111 a. The transistor 112 is provided in the element region 111b.
[0142]
The semiconductor circuit unit 110 may include the processing circuit 113. The processing
circuit 113 may be provided in the element region 111 b or may be provided in other regions.
The processing circuit 113 is provided at an arbitrary place of the semiconductor circuit unit
110. The processing circuit 113 may include the transistor 112 provided in the element region
111 b.
[0143]
The base 71 a is provided, for example, above the semiconductor circuit unit 110. A cavity 70 is
formed in the base 71a. The cavity 70 is formed above the transistor 112. The cavity 70 is
formed at least above the element region 111b. The portion other than the hollow portion 70 in
the base 71 a is the non-hollow portion 71. The non-cavity portion 71 is juxtaposed with the
cavity portion 70 in a plane parallel to the major surface 111a.
[0144]
In this example, the strain sensing element 50 is formed above the substrate on which the
transistor 112 is formed. The transistor 112 and the strain sensing element 50 are connected not
by a wire used in the mounting process, but by a wiring layer formed consistently in the wafer
04-05-2019
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manufacturing process. As a result, the pressure sensor can be miniaturized, and strain can be
detected with high sensitivity in a minute area.
[0145]
By forming the transistor 112 and the strain sensing element 50 on a common substrate, for
example, a circuit (such as the processing circuit 113) that processes information obtained by a
sensor such as an arithmetic circuit, an amplifier circuit, and a communication circuit is distorted.
It can be formed on the same substrate as the sensing element 50. By forming the high
sensitivity sensor integrally with the arithmetic circuit, miniaturization can be realized when
viewed as the entire system. In addition, low power consumption can be realized.
[0146]
In the present embodiment, for example, a high sensitivity sensor is used, and a circuit that
performs arithmetic processing of a signal obtained by the sensor is realized as a system on chip
on a common substrate.
[0147]
However, as described above, the semiconductor circuit unit 110 may be provided separately
from the base 71 a and the sensor unit 72.
In this case, for example, in the package process, the base 71a, the sensor unit 72, and the
semiconductor circuit unit 110 are disposed in one package.
[0148]
FIG. 25A to FIG. 25C are schematic views illustrating the configuration of the pressure sensor
according to the fourth embodiment. 25 (a) is a schematic perspective view, and FIGS. 25 (b) and
25 (c) are block diagrams illustrating pressure sensors.
[0149]
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43
As shown in FIG. 25A, the pressure sensor 361 according to the present embodiment further
includes an antenna 115 and an electrical wiring 116 in addition to the base 71a, the sensor unit
72, and the semiconductor circuit unit 110. The antenna 115 is connected to the semiconductor
circuit unit 110 through the electrical wiring 116. The sensor unit 72 of the pressure sensor 361
has, for example, the same configuration as the sensor unit 72 in the pressure sensor 310
illustrated in FIGS. 1 and 2. That is, for example, the base 71a and the first sensor unit 72A are
provided. The first sensor unit 72A includes a first transducing thin film 64A, a first fixing unit
67A, and a first strain sensing element 50A. In this example, the first sensor unit 72A further
includes a second strain sensing element 50B. These configurations are as described above.
[0150]
As shown in FIG. 25B, the transmission circuit 117 is provided in the pressure sensor 361. The
transmission circuit 117 wirelessly transmits data based on the electrical signal flowing to the
distortion detection element 50. At least a part of the transmission circuit 117 can be provided in
the semiconductor circuit portion 110. The semiconductor circuit unit 110 can include a
transmission circuit 117 that wirelessly transmits data based on an electrical signal flowing to
the strain sensing element 50.
[0151]
As shown in FIG. 25C, the electronic device 118d used in combination with the pressure sensor
361 is provided with the receiving unit 118. For example, an electronic device such as a portable
terminal is used as the electronic device 118d. For example, using the pressure sensor 361
including the transmitting circuit 117 and the electronic device 118 d including the receiving
unit 118 in combination is more convenient.
[0152]
In this example, as shown in FIG. 25B, the pressure sensor 361 is provided with a receiving
circuit 117r that receives a control signal from the electronic device 118d. For example, at least a
part of the reception circuit 117r can be provided in the semiconductor circuit portion 110. By
providing the receiving circuit 117r, for example, the operation of the pressure sensor 361 can
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be controlled by operating the electronic device 118d.
[0153]
As shown in FIG. 25B, in this example, the pressure sensor 361 is provided with, for example, an
AD converter 117a connected to the strain sensing element 50 and a Manchester encoding unit
117b in the pressure sensor 361. Be Furthermore, a switching unit 117c is provided to switch
between transmission and reception. This switching is controlled by the timing controller 117d.
A data correction unit 117e, a synchronization unit 117f, and a determination unit 117g are
provided as the reception circuit 117r. Furthermore, a voltage control oscillator 117h (VCO) is
provided.
[0154]
On the other hand, as shown in FIG. 25C, the electronic device 118d includes a Manchester
encoding unit 117b, a switching unit 117c, a timing controller 117d, a data correction unit 117e,
a synchronization unit 117f, a determination unit 117g, and a voltage control oscillator 117h.
And a storage unit 118a and a central processing unit 118b (CPU).
[0155]
Fifth Embodiment The present embodiment relates to a method of manufacturing a pressure
sensor according to the embodiment.
Hereinafter, a method of manufacturing the pressure sensor 360 will be described as an
example.
[0156]
FIG. 26 is a flowchart illustrating the method for manufacturing the pressure sensor according to
the fifth embodiment. As shown in FIG. 26, in the method of manufacturing a pressure sensor
according to the present embodiment, the transistor 112 is formed on the semiconductor
substrate 111 (step S110).
04-05-2019
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[0157]
In this manufacturing method, the interlayer insulating layer 114i is formed on the
semiconductor substrate 111, and the sacrificial layer 114l is formed on the transistor 112 (step
S120).
[0158]
A thin film (for example, a transducing film 64fm) to be the transducing thin film 64 is formed on
the interlayer insulating film 114i and the sacrificial layer 114l (step S121).
In some cases, the following first conductive layer may also serve as the transducing thin film 64.
In this case, step S121 is omitted.
[0159]
Then, a first conductive layer (conductive layer 61f) to be the first wiring layer 61 is formed (step
S130).
[0160]
The strain sensing element 50 including the first magnetic layer 10 is formed on the first
conductive layer (conductive layer 61f) on the sacrificial layer 114l (step S140).
[0161]
A second conductive layer (conductive layer 62f) to be the second wiring layer 62 is formed on
the strain sensing element 50 (step S150).
[0162]
In the interlayer insulating layer, the first wiring 61 c electrically connecting the first conductive
layer (conductive layer 61 f) to the semiconductor substrate 111 and the second conductive layer
(conductive layer 62 f) electrically connected to the semiconductor substrate 111 Forming a
second wiring 62c (step S160).
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Step S160 is performed, for example, by one or a plurality of processes in the above-described
step S110 to step S150 and / or after step S150.
[0163]
Then, the sacrificial layer 114l is removed (step S170).
[0164]
Then, a confirmation test of the first strain sensing element 50A and the second strain sensing
element 50B is performed (step S180).
For example, the processing described in regard to FIG. 20, FIG. 22 (a) and FIG. 22 (b) is
performed.
[0165]
Then, the first strain sensing element 50A or the second strain sensing element 50B is selected
and fixed (step S190).
For example, the processing described in regard to FIGS. 22 (a) and 22 (b) is performed.
[0166]
According to the method of manufacturing the pressure sensor according to the embodiment,
even when the performance of the transducing thin film 64 varies, it is possible to cope more
flexibly by adopting the applicable strain sensing element 50. Manufacturing efficiency can be
improved.
In addition, a method of manufacturing a highly sensitive pressure sensor can be provided.
04-05-2019
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[0167]
In the step of removing the sacrificial layer 114l (step S170), for example, removing (for
example, etching) the sacrificial layer 114l from the upper surface (the surface of the sacrificial
layer 114l opposite to the semiconductor substrate 111) of the sacrificial layer 114l. Including.
[0168]
Sixth Embodiment FIG. 27 is a schematic view illustrating the configuration of a microphone
according to a sixth embodiment.
As shown in FIG. 27, the microphone 410 according to the present embodiment includes an
optional pressure sensor according to the embodiment and a pressure sensor of a variation
thereof. In this example, a pressure sensor 310 is used. The microphone 410 is incorporated at
the end of the portable information terminal 510. The transducing thin film 64 in the pressure
sensor 360 inside the microphone 410 is, for example, substantially parallel to the surface of the
portable information terminal 510 on which the display unit 420 is provided. However, the
embodiment is not limited to this, and the arrangement of the transducing thin film 64 is
optional.
[0169]
According to the present embodiment, the microphone 410 is sensitive to a wide range of
pressure ranging from low volume to high volume, for example. Therefore, the microphone 410
with a wide dynamic range can be realized. Also, the microphone 410 is highly sensitive to a
wide range of frequencies.
[0170]
The embodiments of the present invention have been described above with reference to specific
examples. However, embodiments of the present invention are not limited to these specific
examples. For example, the person skilled in the art will understand the specific configurations of
the pressure sensor and the microphone included in the substrate, the sensor unit, the
transducing thin film, the fixing unit, the strain sensing element, the magnetic layer, the
04-05-2019
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intermediate layer, and the processing circuit. The present invention is similarly included in the
scope of the present invention as long as the same effect can be obtained by appropriately
selecting from known ranges.
[0171]
Moreover, what combined any two or more elements of each specific example in the technically
possible range is also included in the scope of the present invention as long as the gist of the
present invention is included.
[0172]
In addition, all pressure sensors and microphones that can be appropriately designed and
implemented by those skilled in the art based on the pressure sensor and the microphone
described above as the embodiment of the present invention are also within the scope of the
present invention. Belongs to the range of
[0173]
Besides, within the scope of the concept of the present invention, those skilled in the art can
conceive of various changes and modifications, and it is understood that the changes and
modifications are also within the scope of the present invention. .
[0174]
While certain embodiments of the present invention have been described, these embodiments
have been presented by way of example only, and are not intended to limit the scope of the
invention.
These novel embodiments can be implemented in various other forms, and various omissions,
substitutions, and modifications can be made without departing from the scope of the invention.
These embodiments and modifications thereof are included in the scope and the gist of the
invention, and are included in the invention described in the claims and the equivalent scope
thereof.
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[0175]
DESCRIPTION OF SYMBOLS 10 ... 1st magnetic layer, 10a ... Magnetic laminated film, 10b ... High
magnetostriction magnetic film, 20 ... 2nd magnetic layer, 30 ... Intermediate layer, 41 ... Buffer
layer, 42 ... Antiferromagnetic layer, 43 ... Magnetic layer, 44 ... Ru layer, 45 ... cap layer, 50 ...
strain sensing element, 50A ... first strain sensing element, 50B ... second strain sensing element,
50C ... third strain sensing element, 50D ... fourth strain sensing element, 50a ... strain Sensing
element 50b strain sensing element 50c strain sensing element 50d strain sensing element 50f
laminated film 50s strain resistance change portion 50sg signal 51 first electrode 52 second
electrode 54a ... Insulating layer, 54b ... Insulating layer, 55a ... Bias layer, 55b ... Bias layer, 57 ...
1st wiring, 58 ... 2nd wiring, 61 ... 1st wiring layer, 61bf ... Insulating film, 61c ... 1st wiring, 61f ...
conductive layer, 61 fa ... connection pin 62 62 second wiring 62f conductive layer 62f
connection pillar 62fb connection pillar 64 64 transducing thin film 64A first transducing thin
film 64a film surface 64b ... Center of gravity, 64c ... straight line, 64d ... straight line, 64eg ...
edge, 64fm ... transducing film, 65 ... insulating layer, 65f ... insulating film, 66 ... insulating layer,
66f ... insulating film, 66o opening, 66p ... opening Sections 67: fixing portion 67A: first fixing
portion 67a: fixing portion 67b: fixing portion 67c: fixing portion 67c: fixing portion 70: hollow
portion 70s: substrate 71: non-hollow portion 71a ... base body, 72 sensor part, 72A first sensor
part, 81 multiplexer, 110 semiconductor circuit part, 111 semiconductor substrate, 111a main
surface, 111b. Child regions 112 transistors 112D drains 112G gates 112I element isolation
insulating layers 112M semiconductor layers 112S sources 113 processing circuits 114a
interlayer insulating films 114b interlayer insulating films 114c Connection pillars 114d
connection pillars 114e connection pillars 114f wiring portions 114g wiring portions 114h
interlayer insulation films 114i interlayer insulation films 114j connection pillars 114k
connection pillars 114l sacrificial layers 115 antenna 116 electrical wiring 117 transmission
circuit 117a converter 117b Manchester encoding unit 117c switching unit 117d timing
controller 117e data correction unit 117f synchronization unit 117g determination unit , 117h ...
voltage control source , 117r: reception circuit, 118: reception unit, 118a: storage unit, 118b:
central processing unit, 118d: electronic device, 310: pressure sensor, 321: pressure sensor, 330:
pressure sensor, 331: pressure sensor, 332: ... Pressure sensor, 360 ... pressure sensor, 361 ...
pressure sensor, 410 ... microphone, 420 ... display unit, 510 ... portable information terminal
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