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JPS63237700

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DESCRIPTION JPS63237700
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic transducer, for example, a high-performance, compact, lightweight electrostatic
ultrasonic wave that can be used for detection of a proximity chamber of an industrial robot, a
back sensor of an automobile, etc. It relates to the structure of the transducer. (Conventional art)
Conventionally, in the field of industrial robots, a solid-state image sensor using visible light such
as COD has often been used to recognize the distance, size, shape, etc. of a target object.
However, sensors using visible light have the disadvantage that they can not be used when the
target object is transparent or when the medium between the sensor and the target object is
contaminated with dust or the like. Therefore, in recent years, a technology has emerged that
attempts to use ultrasound for recognition of an object instead of visible light. In ultrasonic
transducers, since ultrasonic waves are transmitted and received by one or more devices, the
mechanical elements that transmit and receive ultrasonic waves, and the electrical circuits such
as the oscillating circuit and receiving circuit that support the mechanical elements. The elements
need to be combined well. In particular, when a surface is vibrated to emit ultrasonic waves into
the air, the response of the air (acoustic impedance) to the surface is very small compared to
liquid or solid, so ultrasonic waves with high intensity can be obtained. Radiation is difficult.
Therefore, it is necessary not only to design ultrasonic waves to be emitted efficiently in the
mechanical elements described above, but also in the electrical elements, it is necessary to
contrive small signals by the amplification compensation circuit and receive them etc. . However,
the ultrasonic transducers generally used at present have a considerable device-to-device
variation in the characteristics of this mechanical element and can not necessarily be designed
optimally. In addition, the mechanical and electrical elements are not integrated into one unit,
which makes it difficult to miniaturize the device. In the following, the prior art will be described
with reference to the drawings, and simultaneously its disadvantages will be described. FIG. 4 is a
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view showing a cross section of a configuration example of a conventional ultrasonic transducer.
In the figure, 47 is a circular aluminum alloy plate, and a plurality of holes 101 having a depth of
several to several tens of pm are formed on the surface by machining. On the upper surface of
the hole 101, a polyester film 48 having a thickness of about 12 pm is sandwiched and fixed by
the metal case 41 and the plate 47 of aluminum alloy. The surface of the aluminum alloy plate
47 and the lower surface of the polyester film 48 are only in point contact with each other. On
the surface of the polyester film 48 opposite to the surface in contact with the aluminum alloy
plate 47, an electrode 49 of gold foil or the like is vapor-deposited.
A protective screen 43 is fixed to the metal case 41 by a protective screen to prevent the
polyester film 48 from being damaged from the outside. On the other hand, a plate spring 46
made of metal is attached to the back surface of the aluminum alloy plate 47, and the aluminum
alloy plate 47 is pressed against the metal case 41. Further, the leaf spring 46 is fixed to the
plastic case 42. The reference numeral 44.45 denotes an electrode terminal, which is integrally
formed with the plate spring 46, while the reference numeral 45 is integrally formed with the
metal case 41. Therefore, the potential of the electrode terminal tool is equal to the plate 47 of
aluminum alloy through the plate spring 46, while the potential of the electrode terminal 45 is
equal to the electrode 49 through the metal case 41. FIG. 5 is a view showing the principle of the
electrostatic ultrasonic transducer described in FIG. 4, which is composed of a mechanical
element 51 for generating vibration and other electric elements 52. The mechanical element 51
is composed of a diaphragm 51a and a fixed plate 51b, and has, for example, a structure [) shown
in FIG. On the other hand, the electric element 52 is drawn and bent by the bias voltage 53, the
resistor 54, the oscillation circuit 55 and the fixed plate 51b in the case of transmission of
ultrasonic waves. Subsequently, when an AC voltage having a smaller amplitude than the bias
voltage 53 is applied to the oscillation circuit 55, the polarity changes according to the polarity
of the voltage at both ends of the oscillation circuit 55 as follows. That is, when the polarity of
the voltage applied to both ends of the oscillation circuit 55 is the same as the bias voltage 53,
the deflection of the diaphragm 51a becomes large because a potential difference equal to the
sum of these voltages is applied to the diaphragm 51a and the fixed plate 51b. On the other
hand, when the polarity of the voltage of the oscillation circuit 55 is opposite to that of the bias
voltage 53, the deflection of the diaphragm 51a is reduced because a potential difference equal
to the difference between these voltages is applied to the diaphragm 51a and the fixed plate 51b.
Therefore, when the voltage across the oscillating circuit is periodically changed by the
oscillating circuit 55, the diaphragm 51a vibrates and an ultrasonic wave is emitted to the front.
The resistor 54 has a function of protecting the circuit so that a large current does not flow in
the circuit when a discharge or the like occurs between the diaphragm 51a and the fixed plate
51b. Although the case of transmitting the ultrasonic wave has been described above, in the case
of delivery, it is sufficient to flash the receiving circuit 55 for performing amplification
compensation etc. in FIG. At this time, the diaphragm 51a vibrates due to the ultrasonic wave
that has entered from the outside, and the capacity between the diaphragm 51a and the fixing m
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51b changes. Therefore, an alternating current flows in the receiving circuit 55, and
amplification can be compensated for the delivery of ultrasonic waves.
(Problems to be Solved by the Invention) In the above, the description has been made of the
conventional electrostatic ultrasonic transducer using an example. Among them, when machining
the hole 101 shown in FIG. 4, some variation in the size and shape of the hole can not be avoided
by the conventional machining method. This hole 101 corresponds to the gap between the
vibration Fi 51a and the fixed plate 51b shown in FIG. 5, and when the size and the outer shape
vary, the driving force of the diaphragm 51a varies and eventually the transmission and
reception of ultrasonic waves. There is a drawback that the wave characteristic is not constant. In
addition, when the thickness of the polyester film 48 (FIG. 4) is reduced, minute holes are
produced in the film due to manufacturing, and the high bias voltage 53 (FIG. 5) makes the
electrode 49 and the aluminum alloy plate A discharge occurred between 47 and 47, which often
caused deterioration of the device characteristics. For this reason, the thickness of the polyester
film 48 is limited, and there is a problem that the freedom of design is restricted. 1 Furthermore,
as described above, in the ultrasonic transducer, the combination of mechanical and electrical
elements is inevitable, and it is intended to realize a higher performance device by using a
conventional structure. As a result, the area occupied by this electrical element has become
larger and there has been a tendency that the apparatus becomes larger. In fact, the wires
connecting the electrodes of the arrayed transducers are known to be quite large by themselves.
As described above, in the prior art, there is a disadvantage that the device can not be reduced in
size and weight even if a device with higher performance is manufactured. An object of the
present invention is to eliminate the drawbacks of the prior art and to provide a highly sensitive,
compact and lightweight ultrasonic transducer having uniform characteristics. (Means for
Solving the Problems) According to the present invention, an organic thin film having a first
electrode on one surface and a second electrode provided on the surface of a semiconductor
substrate having a hole on the surface An ultrasonic transducer, comprising: an ultrasonic
transducer provided between the first electrode and the second electrode so as to be fixed to the
surface of the second electrode; and An organic thin film having a first electrode on the surface
and one semiconductor substrate having a hole on the surface □ 4. よ1.、ゎえやユ。 In the
91 □ E □ □ 8 wave transducer, a plurality of ultrasonic transducers provided between the first
electrode and the second electrode so as to fix the insulating film on the surface of the second
electrode are arranged in an array. An ultrasonic transducer can be obtained, which is capable of
inputting and outputting independent electrical signals to electrodes on at least one of the first
and second electrode sides of the individual ultrasonic transducers.
(Operation) The ultrasonic transducer of the present invention is an electrostatic ultrasonic
transducer capable of integrating a manufacturing method and peripheral circuits conforming to
IC process technology such as silicon, as shown in FIG. 2, an elastic vibrator. The ultrasonic wave
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is transmitted by moving the organic thin film processing 0, which is the above and below, up
and down according to the change in the potential difference applied to the upper and lower
electrodes of the CVD 5102 film 3 provided on the silicon substrate l. On the other hand, when
this device is used for delivery of ultrasonic waves, the organic thin film 10 vibrates due to the
pressure of the external ultrasonic wave, and as a result, the capacitance between the upper and
lower electrodes of the CVD 5 i O □ film 3 changes. By fixing the edge film by oxidation, CVD,
sputtering, coating or the like, it is possible to reduce the distance between the upper electrode
49 and the lower electrode 6 while maintaining good insulation between the upper electrode 49
and the lower electrode 6. In addition, since the ultrasonic transducer according to the present
invention uses a semiconductor substrate, (1) holes can be precisely formed on the
semiconductor substrate using the fine etching technique of the semiconductor, and variations in
device characteristics resulting from the manufacturing process (2) The oscillation circuit and the
reception circuit can be integrated using semiconductor IC process technology, and thus it
becomes possible to manufacture a high-performance ultrasonic transducer in a small size and
light weight. EXAMPLE An electrostatic airborne ultrasonic transducer, which is a type of
ultrasonic transducer, will be described below with reference to the drawings. している。 An
upper electrode 49 made of gold, aluminum or the like is vapor-deposited on the lower surface of
the organic thin film 10 such as a polyester film that transmits and receives ultrasonic waves in
the present embodiment. The organic thin film 10 vibrates up and down on the unpenetrated
etching hole 12 opened in the silicon substrate 1 and when the wave is generated, a voltage is
generated by the organic thin film 10 vibrating. A CvDSiO2 film 3 is provided on one main
surface of the silicon substrate 1 between the lower electrode 6 and the upper electrode 49 as
shown in FIG. This helps to maintain the electrical insulation between the upper electrode 49 and
the lower electrode 6. Furthermore, when the thickness of the CVD SiO 2 film 3 is about lpm, the
spatial distance between the upper electrode 49 and the lower electrode 6 is also about lpm, and
as shown in FIG. The distance between the electrodes is significantly reduced compared to the
thickness of the polyester film 48, which is about 12 pm)-the configuration allows the distance
between the electrodes to be reduced, which results in The sensitivity of the transmission and
reception characteristics of the device can be increased.
The SiO □ film 20 is also inserted between the lower electrode 6 and the silicon substrate 1 to
prevent the current from leaking between the lower electrode 6 and the silicon substrate l. The
lower electrode 6 is electrically connected to the integrated circuit 8 for drive and reception
fabricated on the silicon substrate 1 via an aluminum wiring (not shown) also placed on the CVD
5102 film 3 . Further, the etching holes 12 are manufactured by applying, for example, an
anisotropic etching technology of silicon in order to finish the size and shape with high accuracy.
This is, for example, a photolithographic technique for forming patterns of a plurality of square
SiO 2 films in which the side is aligned in the <110> direction on one surface of the silicon
substrate 1 having the main surface in the (100) direction. After formation using the sample, the
sample is immersed in an anisotropic etching solution such as hydrazine. In this case, there is a
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feature that the etching of silicon automatically stops at the stage where the etching hole 12 in
the shape of a pyramidal square pyramid is formed. It also has the advantage of being able to
process a large number of samples at one time as mentioned above. FIG. 3 shows an example of
the procedure for producing an ultrasonic transducer having an embodiment of the present
invention. In the drawings, the same reference numerals as in FIGS. 1 and 2 shown as one
embodiment of the present invention denote the same components. The same figure (a) is the
same shape as the etching hole 12 of the said FIG. 1 using the photolithographic technique for
what put the silicon substrate 1 with a (100) plane in the oxidation furnace, and put 8102 film
20 on the front and back. A square opening 30 having a length of several tens of μm is formed
on one side of. When forming the opening 30, it is necessary to arrange so that the side of the
etching hole 12 in FIG. 1 faces in the <110> direction. This sample is immersed in an aqueous
solution such as EDP (ethylenediamine pyrocatechol) or hydrazine to perform anisotropic etching
of silicon (FIG. 6B). An aqueous solution such as FDP or hydrazine has the property that the
etching rate to the (100) plane is significantly larger than the etching rate to the (111) plane of
silicon (oxidize the sample again to attach the 8102 film 20 to the anisotropic hole 12) Then, the
integrated circuit 8 for transmission and reception is formed by using a normal silicon IC process
technology (FIG. 2C). Subsequently, an aluminum thin film serving as a lower electrode 6 and a
wire (not shown) connecting the same to the integrated circuit 8 is formed on the SiO □ film 20
by evaporation or the like, then the sample is put in a CVD furnace and the CVD 5102 film 3 is
formed. It forms (the figure (d)).
The lower electrode is preferably made of Au on the Cr underlayer in order to improve the
bonding with the 5iO 9 film 20. However, the lower electrode is not necessarily limited to this,
and a metal such as aluminum may be substituted Also good. Thereafter, the organic thin film 10
on which the upper electrode 49 is vapor-deposited is adhered to the CvDSio2 film 3, and then
the device is mounted on a package (FIG. 3E). In the embodiment of the present invention shown
in FIGS. 1 and 2, the structure in which the upper electrode 49 is in direct contact with the CVD
film 5 is shown. On the other hand, a configuration similar to that of the conventional example
shown in FIG. 4 by reversing the positional relationship between the upper electrode 49 and the
organic thin film 10 is also included in the present invention. In this case, there is a disadvantage
that the sensitivity is lower than that of the previous example, but the upper electrode 49 and the
lower electrode 6 are formed by the CVD Si 2 film 3 provided between the organic thin film 10
and the lower electrode 6. Can be made thinner, so the sensitivity can be increased. In addition,
since the thickness of the organic thin film can be made thick or thin, there is an advantage that
design freedom is increased. 6 and 7 are plan views showing other embodiments of the present
invention. In the figure, the same reference numerals as in FIGS. 1 and 2 denote the same
components. In these embodiments, a rectangle 70 indicated by a broken line indicates elements
included on the same lower electrode shown in FIGS. 1 and 2. However, integrated circuit 8 is not
included. Further, the electrodes formed on the upper and lower surfaces of the vibrator element
70 are connected to a part of the peripheral circuit 8 through an aluminum wiring (not shown).
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As shown in the embodiment of FIGS. 6 and 7, when a plurality of the vibrator elements 70 are
arranged, the ultrasonic wave is strongly emitted at a small angle of the front surface or the
ultrasonic wave of only a small angle of the front surface is strongly received. It is characterized
in that it is possible to reduce the risk of being confused by surrounding noise. Also, using the
technique of anisotropic etching of silicon described above, vibrator elements 70 of exactly the
same shape are simultaneously formed. In addition to the embodiment shown here, there is also
an embodiment in which the area of the central oscillator element 70 is increased and the area of
the oscillator element 70 is decreased toward the periphery (not shown). In this case, there is an
advantage that the directivity described above is further improved, and a high quality device with
less noise can be provided. FIG. 8 is a plan view of the second embodiment of the present
invention. In the figure, the same reference numerals as in FIG. 6 indicate the same components.
The embodiment of the present invention is characterized in that the lower electrodes 6 formed
on the vibrator element 70 are disposed separately from each other, and are connected to the
peripheral circuit 8 through aluminum wiring, respectively.
Therefore, in the ultrasonic transducer having the configuration of the present embodiment, it is
possible to apply voltages having different strengths and phases to the respective vibrator
elements 70. In particular, by applying a voltage having a different phase to each of the oscillator
elements 70, it is possible to change the direction of transmission and reception of ultrasonic
waves, and thus, high-performance ultrasonic waves that electrically scan. It is possible to realize
a device having the same effect as the above even if the electrodes 49 on the upper surface of
each vibrator element 70 are separated for each vibrator element 70. Although FIG. 8 shows an
ultrasonic transducer array of one row and five columns, the number of vibrator element 70
need not be limited at all. For example, in the embodiment of FIG. 7, when the electrodes on the
upper and lower surfaces of the vibrator element 70 are arranged separately for each vibrator
element 70 and each electrode is connected to the peripheral circuit 8, it is possible to
electrically connect in two dimensions. A two dimensional ultrasound transducer that can be
scanned can be realized. Further, in the ultrasonic transducer array described in the present
embodiment, the lower surface electrode of each vibrator element 70 can be simultaneously and
easily formed using the normal IC process technology, which is also larger than the prior art. It is
an advantage. In the embodiment in which the lower electrode or the upper electrode is
separated, one vibrator element 70 is described as having a plurality of etching holes as shown in
FIG. 1 and FIG. 2, but the present invention is not limited thereto. Whether the ultrasonic waves
corresponding to one vibrator element continuously change, or pulsatively changes only at a few
wavelengths, etc., in the etching holes in FIGS. It holds true. In addition, regardless of whether the
wavelength of ultrasonic waves is single or plural, the same holds true. In the embodiments of
the present invention, air was confined in the lower part of the vibrating body, but in addition to
this configuration, an open hole is formed at the bottom of the hole to allow air flow. is there.
Furthermore, the present invention reduces the influence of the back side of the device by
placing a sound absorbing material such as a sponge outside the hole and the like, and the
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configuration in which the horn is placed in front of the vibrator to increase the sensitivity.
include. The sensitivity of the transmission and reception of ultrasonic waves can be increased by
increasing the area of the organic thin film contributing to vibration or reducing the thickness in
the above embodiment. Furthermore, the sensitivity can also be increased by thinning the
CvDSi02 film 3 between the organic thin film and the lower electrode.
However, in this case, the ultrasonic sensor is not designed because changes in the frequency
characteristics of the device and the like occur simultaneously. Although the CVD 5102 film 3
shown in FIG. 2 is used as the insulating film in the above embodiment, the film is not limited to
Koreni, but may be 513N4.5iO1Ny, polyimide or the like on the surface of the lower electrode 6
such as polyimide. Any material that can be fixed in a thin film by a method such as sputtering or
coating can be used. (Effects of the Invention) As described above, according to the present
invention, it has become possible to supply an integrated ultrasonic transducer with high
sensitivity, small size and light weight with less variation in characteristics. As a result, it has
become possible to use a high-performance ultrasonic transducer for the detection of a proximity
room etc. in the field of industrial robots etc. Since the ultrasonic transducer of the present
invention can be manufactured in large quantities by a manufacturing method consistent with
the conventional semiconductor IC manufacturing process technology, the manufacturing cost
can be reduced. These effects are remarkable, and the present invention is effective.
[0002]
Brief description of the drawings
[0003]
1 and 2 are sectional views of-of the first invention of the present application, FIG. 5 is a
principle view of a conventional electrostatic transducer, and FIGS. 6 and 7 are other than the
first invention of the present invention. FIG. 8 is a plan view showing an embodiment of an
ultrasonic transducer array according to the second invention of the present application.
DESCRIPTION OF SYMBOLS 1 ... silicon substrate, 3 ... CVD5102 film, 6 ... lower electrode, 8 ...
integrated circuit, 10 ... organic thin film, 12 ... etching hole, 20 "-5iOz film, 30 --Opening, 41-Metal case, 42-Plastic case, 43-Protective screen, 45,-Electrode terminals, 46-Leaf springs, 47Aluminum alloy plates , 48: polyester film, 49: upper electrode, 51: mechanical element, 51a:
diaphragm, 51b: fixed plate, 52: electrical element, 53: Bias voltage, 54: resistance, 55:
transmission and reception circuit, 70: vibrator element.
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