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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to
ultrasonic sensors → no, and relates to ultrasonic sensors of the capacitor type on bamboo. A
condenser-type ultrasonic sensor is known as a type of ultrasonic sensor (see the prior art and
the intervening point) -S. This is a sensor that is mainly used as a distance measurement sensor,
and is formed by a polymer film with a 金属 metal electrode on the surface and a (2) electrode
set apart from the polymer film and a certain space. Ru. Conventionally, the above-mentioned
condenser type ultrasonic sensor is mainly used for distance measurement, and it is necessary to
measure the delay time until the ultrasonic wave emitted from the surface of this sensor reflects
on the front object and returns to the sensor. The distance between the sensor and the east
object can be determined from the formula%. As this distance measurement ultrasonic sensor, a
condenser ultrasonic sensor used in Polaroid's automatic 4B <point camera b + · is well known.
This Polaroid ultrasonic sensor has a structure in which a polymer film having thin metal
electrodes provided on its surface is pressed against the surface of an aluminum disk in which
concentric grooves are formed. The front surface of the polymer film and the back surface of the
aluminum respectively act as electrodes and are easily connected electrically to the outside. Thus,
the capacitor type ultrasonic sensor is characterized by its simple structure. However, in the case
of ultrasonic imaging in which a plurality of condenser type ultrasonic sensors are arranged in an
array and the relative phase of the ultrasonic waves sent out from each sensor is changed to scan
the ultrasonic waves, the conventional condenser type ultrasonic waves It was difficult to use the
sensor. That is, in the ultrasonic scanning sensor array, the width of each of the ultrasonic
sensors constituting the array needs to be as small as the wavelength of the ultrasonic wave to be
used. For example, the wavelength in the air of ultrasonic waves with a frequency of 100 kHz is
about 34, and arranging the conventional capacitor-type ultrasonic sensors in the size of a
wavelength or so increases the assembly process significantly. There was a drawback. (Object of
the Invention) An object of the present invention is to provide a capacitor-type ultrasonic sensor
which eliminates such conventional drawbacks and is suitable for arraying sensors. According to
the present invention, according to the present invention, a thin metal electrode comprises a
polymer film provided on the surface and a signal input electrode provided spaced from the
polymer film by an alternating current voltage applied between the electrodes. The polymer film
vibrates to generate an ultrasonic wave, and when the ultrasonic wave enters the polymer film,
the capacitance between the electrodes changes to detect the ultrasonic wave. In the sensor, the
signal input electrode is n-type silicon A polymer film provided in a recess formed on one side of
the substrate and provided with the thin metal electrode on the surface is provided to cover the
recess, and the signal input electrode penetrates the n-type silicon substrate It is characterized in
that it is taken out to the other side by the v-type layer, and one ultrasonic sensor is obtained.
The present invention will be described below with reference to the drawings showing the
embodiments. FIG. 1 is a sectional view showing an embodiment of the present invention, in
which 1 is an n-type silicon substrate, 2 is a P + type silicon, 3 is an insulator, 4 is a signal input
electrode, and 5 is a polymer such as polyester. A film 6 is a metal electrode such as gold, 7 is a
signal terminal, 8 is a ground terminal, and 9 is n + -type silicon. The signal input electrode 4 is
provided on the n-type silicon wafer in a region anisotropically etched from the back surface with
the insulator 3 interposed. Generally, when silicon is etched anisotropically with potassium
hydroxide (KOH) solution or hydrazine solution using silicon oxide (Sin) film or silicon nitride
film as a mask, the dimensional accuracy of the etching area is isotropic etching It is possible to
obtain an array with a high degree of uniformity and a high degree of characteristics.
Furthermore, the signal input electrode 4 is connected to the signal terminal 7 on the silicon
surface via l) + type silicon 2. In this wedge-shaped silicon, aluminum (A7) having a
predetermined shape is provided to a thickness of about 5 μm on the silicon surface, and then
the aluminum travels through the silicon by heating the silicon back surface by light irradiation
(Anthony (T, R, A, nthony). クライン(H,E、CItne);ジャーナルオブアプライドフィツ
クス(J、Appl、phys、)、vo147 no、6.p、2316. It can be easily
formed using (1976). (Effects of the Invention) Since the upper and lower surfaces of the silicon
substrate 1 with a thickness of 100 μm to 500 μm are electrically connected in this way, the
signal input electrode 4 which is one electrode of the capacitor type ultrasonic sensor is It is only
necessary to form the polymer film 5 provided on the silicon surface by the signal terminal 7
provided on the silicon surface and provided with the metal electrode 6 on the back surface of
the silicon, and the assembly is simplified. When arrayed, the respective signal terminals are
electrically separated by the insulator 3 and the pn junction of the silicon 2 and the n silicon 1.
The n + -type silicon 9 and the ground terminal 8 are for grounding the n-type silicon 1. FIG. 2 is
a plan view of FIG. 1 and shows that a signal terminal 7 and a ground terminal 8 are provided on
the silicon surface. From the figure it can be seen that most of the area of the silicon surface can
be further used to form, for example, a breathing circuit such as an ultrasonic sensor drive circuit
or a receiver circuit. FIG. 3 is a cross-sectional view of the case where the ultrasonic sensors
shown in FIG. 1, which is an embodiment according to the present invention, are arrayed. A
plurality of capacitor type ultrasonic sensors are formed in an array in a silicon wafer, and these
can be manufactured with high accuracy by using a photolithographic technology in silicon IC
manufacturing technology.
In the present invention, in addition to an array of dimensions, it is also possible to arrange
ultrasonic sensors two-dimensionally in a silicon plane.
Brief description of the drawings
FIG. 1 is a cross-sectional view of an embodiment according to the present invention, FIG. 2 is a
plan view of FIG. 1, and FIG. 3 is a cross-sectional view of an embodiment in which capacitor type
ultrasonic sensors according to the present invention are arranged in an array. is there.
In the figure, 1 is n-type silicon, 2 is P + m silicon, 3 is an insulator, 4 is a signal input electrode,
5 is a polymer film, 6 is a metal electrode, 7 is a signal terminal, 8 is a ground terminal, 9 is n +,
Indicates silicon. Agent ヅ r 理 inside jT 晋 5. .
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