JPS61220598A - Ultrasonic wave transducer - Google Patents

Abstract

PURPOSE:To manufacture a highly efficient and small product by facing the first electrode which is provided on the one surface of a diaphragm that is performed with an inorganic insulation film and the compound layer of a high polymer film with the second electrode through a spacer that is constituted with silicon. CONSTITUTION:A diaphragm 22 is performed with an inorganic insulation film 1, for example SiO2 etc., and a high polymer film 2 that is constituted with polyimide resin etc. and an electrode 3 is laminated by evaporating gold etc. on the diaphragm. With providing an electrode 4 on an insulation case 5, a spacer which is constituted with a silicon substrate 9 keeps a prescribed space between the diaphragm 22 and the electrode 4. An oscillating and receiving circuit 8 is integrated by a process technique at the contacting part of the silicon substrate 9 and the diaphragm 22. The silicon substrate 9 and the electrode 4 are adhered with gold/silicon eutectic alloy 13. Leads 10 and 11 input and output a signal between the integrated circuit 8 and the outside through a bonding wire 6 and an aluminum wire 7. Thus, a small and highly efficient product is manufactured. This is most appropriate for an industrial robot.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an ultrasonic transducer, and in particular to a high performance, small and lightweight ultrasonic transducer that can be used to detect a nearby room of an industrial robot. Concerning the structure (Prior art and its problems) Conventionally, in the field of industrial robots, solid-state image sensors such as CCDs that use visible light are often used to recognize the distance, size, shape, etc. of target objects. It's here.

However, sensors that use visible light have the disadvantage that they cannot be used when the target object is transparent or when the medium between the sensor and the target object is dirty with dust or the like. Therefore, in recent years, a technology has appeared that attempts to use ultrasonic waves instead of visible light to recognize target objects. In an ultrasonic transducer, ultrasonic waves are transmitted and received by one or more devices, so there are mechanical elements that oscillate and receive ultrasonic waves, and electrical elements such as oscillation circuits and reception circuits that support this. It is necessary to properly combine the elements. In particular, when trying to emit ultrasonic waves into the air by vibrating a certain surface, the response (acoustic impedance) of the air to that surface is very small compared to liquids or solids, so ultrasonic waves with high intensity are emitted. is difficult. Therefore, it goes without saying that the mechanical elements mentioned above should be designed so that ultrasonic waves are emitted efficiently.
Even in the electrical elements, it is necessary to take measures such as compensating for small signals using an amplification compensation circuit for reception. However, in the currently commonly used ultrasonic transducers, the mechanical element and the electrical element are separated from each other. Hereinafter, a conventional example will be explained with reference to figures, and at the same time, its drawbacks will be discussed.

FIG. 4 is a cross-sectional view of an example of the configuration of a conventional ultrasonic transducer. In the figure, reference numeral 47 denotes a circular aluminum alloy plate, in which a groove 101 having a depth of several tens to hundreds of μm is formed in the center. The upper surface of this groove 101 has a thickness of 6 to 20 μm.
A polyester film 48 having a diameter of m is inserted and fixed between a metal case 41 and an aluminum alloy plate 47. On the surface of the polyester film 48, four electrodes made of gold foil or the like are deposited on the surface opposite to the surface in contact with the aluminum alloy plate 47. 43 in the figure is a protective screen fixed to the metal case 41 to prevent the polyester film 48 from being damaged from the outside. On the other hand, a plate spring 4G made of metal is attached to the back surface of the aluminum alloy plate 47, and presses the aluminum alloy plate 47 against the metal case 41. Further, the leaf spring 46 is fixed to the plastic case 42. 44 and 45 are electrode terminals, and 44 is the leaf spring 4.
6, while 45 is constructed integrally with metal case 4.
It is constructed integrally with 1. Therefore, the potential of the electrode terminal 44 is equal to that of the aluminum alloy plate 47 via the plate spring 46, while the potential of the electrode terminal 45 is equal to that of the electrode 49 via the metal case 41.

From this, when a voltage is applied to the electrode terminals 44, 45, a voltage equal to this applied voltage is generated between the aluminum alloy plate 47 and the electrode 49, and the polyester film 44 due to electrostatic force.
Flex 8. Therefore, when the voltage applied to the electrode terminals 4-4, 45 changes with alternating current, the electrostatic force acting on the polyester membrane 48 also changes with alternating current, causing the polyester membrane 48 to vibrate, and as a result, ultrasonic waves are transmitted to the front surface. is radiated to. FIG. 5 is a diagram showing the principle of the electrostatic ultrasonic transducer described in FIG. Reference numeral 51 is composed of a diaphragm 51a and a fixed plate 51b, and has the structure shown in FIG. 4, for example. on the other hand,
The electric element 52 includes a bias voltage 53, a resistor 54, and an oscillation circuit 55 when transmitting ultrasonic waves. now,
When no signal is generated from the oscillation circuit 55, the diaphragm 51a is pulled toward the fixed plate 51b by the bias voltage 53 and is bent. Subsequently, the bias voltage 53 is applied to the oscillation circuit 55.
If an alternating current voltage smaller than
It changes as follows depending on the polarity of the voltage generated across the . That is, when the polarity of the voltage generated across the generator circuit 55 is the same as the bias voltage 53, a potential difference equal to the sum of these voltages is applied to the diaphragm 51a and the fixed plate 51b, so that the flexure of the diaphragm 51a increases. . On the other hand, when the polarity of the 7 pressure of the oscillation circuit 55 is opposite to the bias voltage 53, a potential difference equal to the difference between these voltages is applied to the diaphragm 51a and the fixed plate 51b, so the deflection of the diaphragm 51a is small. Become. Therefore, when the oscillation circuit 55 periodically changes the voltage across the oscillation circuit, the diaphragm 51a vibrates and ultrasonic waves are emitted to the front. Note that the resistor 54 has a function of protecting the circuit so that a large current does not flow in the circuit when discharge or the like occurs between the diaphragm 51a and the fixed plate 51b. Although the case of ultrasonic wave transmission has been described above, in the case of wave reception, it is preferable to replace 55 in FIG. 5 with a receiving circuit that performs amplification compensation and the like. At this time, the diaphragm 51a vibrates due to the ultrasonic waves that entered from the outside, and the diaphragm 51a vibrates.
The capacitance between a and the fixed plate 51b changes. Therefore, an alternating current flows through the receiving circuit 55, and by amplifying and compensating this current, it becomes possible to receive ultrasonic waves. The conventional electrostatic ultrasonic transducer has been described above using examples. As shown here, in an ultrasonic transducer, a combination of mechanical and electrical elements is inevitable, and even in the conventional ultrasonic transducer shown in FIG. The whole was constructed by adding an external electric circuit to the mechanical elements shown in Figure 4. Therefore, when trying to realize a high-performance device with a conventional structure, the area occupied by the electrical elements becomes larger and larger, and there is a tendency to make the device larger.

This trend has become an increasing problem when attempting to implement ultrasonic transducer arrays. It is known that the wiring connecting the electrodes of an array of transducers becomes quite large. On the other hand, as mentioned above, high performance and compact ultrasonic transducers are needed in the field of industrial robots. Therefore, there is a strong need for a small and lightweight device that integrates the electrical elements of an ultrasonic transuser using silicon IC process technology, and molds these and the mechanical elements that produce vibration into one piece. Ta. However, ultrasonic transducers with conventional structures have the disadvantage that it is impossible to manufacture mechanical components that match silicon IC process technology, and therefore it is not possible to reduce the size and weight of the device. Ta.

(Object of the Invention) An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and to provide a high performance, small and lightweight ultrasonic transducer.

(Structure of the Invention) According to the present invention, the diaphragm is composed of a diaphragm having a first electrode on one side of its surface, and a second electrode facing the diaphragm with a spacer interposed therebetween, and the spacer is made of silicon. An ultrasonic transducer comprising: a diaphragm having a first electrode on one side of its surface; and a second electrode facing the diaphragm with a spacer interposed therebetween. One element is an ultrasonic transducer in which the electrostatic spacer is made of silicon, a plurality of such elements are arranged on the same silicon substrate, and at least one of the first or second electrode is connected to the ultrasonic transducer. An ultrasonic transducer is obtained in which each element is separated and a different voltage is applied to the diaphragm of each element.

(Principle of operation of the invention) The ultrasonic transducer of the present invention is a monolithic ultrasonic transducer that enables integration of peripheral circuits and a manufacturing method compatible with silicon IC process technology.
As shown in the figure, a diaphragm made of a polymer membrane with a small elastic constant as the main body 6 is deformed in accordance with changes in the potential difference applied to the upper and lower electrodes, and is devised to transmit ultrasonic waves. When this device is used to receive ultrasonic waves, the capacitance between the upper and lower poles of the diaphragm changes when the diaphragm vibrates due to external ultrasonic waves. This is designed to be able to rise as a result of strange changes in the current.

In addition, since the spacer hS silicon is inserted between the diaphragm and the lower chisel pole, the 111. ! Since the circuit and the receiving circuit can be integrated using IC process technology, a high-performance ultra-bamboo wave transducer can be manufactured with a small volume.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. 1171 is a sectional view showing one embodiment of the present invention, and FIG. 2 is a conceptual diagram showing the operating principle of the present invention. In the figure, the same numbers as in FIGS. 4 and 5, which are shown as conventional examples, indicate the same components. The diaphragm 22 that transmits and receives ultrasonic waves in this embodiment is made of a thin inorganic insulating film 1 made of silicon dioxide (Sin, etc.) and a film of several to 20 μm.
Since it is composed of a polymer film 2 made of polyimide resin or the like having a thickness of m, it has a small elastic constant, and therefore has a structure that is easily deformed by vibration.

In addition to this example, the film 1 is a silicon nitride film (8i3
N4) or S i 3 N4/8 tOv/S +
A three-layer structure film of 3N4 or the like may be used, and has the role of protecting the polymer film 2 when the groove 12 is formed by chemically etching the silicon substrate 9. Further, the thickness of the polymer film 2 can be precisely controlled by using a spin coating method, and photoresist may be used as a material other than this embodiment. On one surface of the diaphragm 22 having such a structure, gold or the like is applied by vapor deposition or the like to form the first electrode 3. On the other hand, on the back side of the diaphragm 22, a second electrode 4 is attached on an insulating case 5 made of Bakelite or the like, facing the first electrode 3. It has a structure in which the diaphragm 22 and the silicon substrate 9 are inserted through the electrode 4. The silicon substrate 9 no longer serves as a spacer between the diaphragm 22 and the second electrode 4, and on the surface in contact with the diaphragm 22, an eye development and reception circuit indicated by 8 is integrated using IC process technology. There is. Further, on the surface of the silicon substrate 9 opposite to the surface on which the diaphragm 22 is formed, the silicon substrate 9 is bonded to the electrode 4 and the insulating case 5 using a gold-silicon eutectic alloy 13 or the like. Reference numerals 10 and 11 in the figure are leads for inputting and outputting signals between the integrated circuit 8 and an external power supply and control device (not shown) via bonding wires 6 and aluminum wiring 7, respectively.

Note that the lead 11 is connected to the second electrode 4 as shown in the figure, and the electrode 4 is connected to the terminal of the integrated circuit 8.
It gives a potential equal to . FIG. 2(a) shows a case where the polarity of the voltage generated across the oscillation circuit 55 is opposite to the bias voltage 53, and FIG. 2(b) shows a case where the polarity of the voltage is the same. . As shown in the figure, the diaphragm 22 is displaced more in the figure (b) than in the figure (a). Therefore, when the voltage of the oscillation circuit 55 changes in an alternating current manner and changes its polarity, the diaphragm 22 deforms as shown in the figure (1→(b)→(a)→...), and as a result, Ultrasonic waves are emitted to the front surface of the diaphragm 22. The intensity of the ultrasonic waves is stronger as the bias voltage 53 becomes larger, but on the other hand, when the bias voltage 53 is too large, the ultrasonic waves are There is a risk that the device will be damaged due to the occurrence of discharge.Therefore, the bias voltage 53 should be designed to an appropriate value.As mentioned earlier, when the device is used to receive ultrasonic waves, 2, it is recommended to replace 55 in Fig. 2 with an appropriate receiving circuit.At this time, since the capacitance between the first electrode 3 and the second electrode 4 changes according to the deformation of the diaphragm 22, it is better to replace 55 in Fig. 2 with an appropriate receiving circuit. Ultrasonic wave is diaphragm 2
2 is transformed from (a) to (b) to (a) in the figure, the value of the current flowing across the receiving circuit 55 changes.

By subjecting this current value to appropriate signal processing by the receiving circuit 55, it becomes possible to receive ultrasonic waves. Note that the transmitting circuit and receiving circuit described in this embodiment are not particularly limited, and it goes without saying that the present invention includes all known circuit techniques.

FIG. 3 shows an ultrasonic transgy having an embodiment of the present invention.
This figure shows an example of a procedure for manufacturing a sachet. Same figure (,
) is one in which a peripheral circuit 32 is formed on the surface of a silicon substrate 30 using normal silicon IC process technology. At this stage, since the oxide film 31 is normally formed on the front and back surfaces of the silicon substrate 30, the oxide film 31 is completely removed by etching (FIG. 3(b)). Next, an oxide film 31 is formed on the front surface of the silicon substrate 30 by the CVN method (FIG. 2(C)), and a thin oxide film is further formed on the front and back surfaces of the silicon substrate 30 by a thermal oxidation method (FIG. 1(D)). )). The reason for performing the above procedure is to suppress the stress generated in the oxide film 31 on the front surface of the silicon substrate 30, and to ensure that etching stops at the oxide film 31 at the stage shown in FIG. It is necessary to do so. Now, polyimide resin or the like is spread on the surface 1111 of the silicon substrate 30 (fd) in the same figure by rotation, and this is baked and hardened to form a polymer 1111. After that, it is protected with a photoresist or the like and the peripheral circuit 32 is formed. A contact hole 34 is made to take out the electrode to the outside (FIG. 4(e)). Subsequently, after aluminum or the like is deposited on the front side of the silicon substrate 30, unnecessary portions are removed to form electrodes 35 and aluminum wiring 38 (FIG. 3(f)). The oxide film 31 in the region l of the groove pattern 36 is removed from the back side of the silicon substrate 30 (same l;
4(g)). Thereafter, the groove 37 is formed by etching the silicon substrate 30 using a jig so that only the back side of the silicon substrate 30 comes into contact with the etching solution. At this time, if an anisotropic etching solution such as KOH or hydrazine is used as the silicon etching solution, there will be no unnecessary etching in the lateral direction, and the grooves 37 can be formed with precise control. . Note that when a large stress exists in the oxide film 31 formed on the front side of the silicon substrate 30, cracks occur in the oxide film 31 covering the groove 37 when the groove 37 shown in FIG. It happens that the polymer film 33 is etched through this crack. Therefore, care must be taken not to generate large stress on the oxide film 31 on the front side of the silicon substrate 30.

FIGS. 6 and 7 are plan views showing other embodiments of the present invention. In the figure, the same numbers as in FIG. 1 indicate the same components. In these examples, the dashed rectangles represent diaphragms 22. Also,
The electrode 3 formed on the upper surface of the diaphragm 22 is connected to the peripheral circuit 8 through the aluminum wiring 60 and the contact hole 61.
connected with some of the In addition, in these figures,
The aluminum wiring connecting the peripheral circuits 8 is omitted in the drawing. When a plurality of diaphragms 22 are lined up as shown in the embodiments of FIGS. 6 and 7, it is possible to strongly radiate ultrasonic waves at a small angle on the front surface, or to strongly receive ultrasonic waves only at a small angle on the front surface. It has the advantage of being less distracting from surrounding noise. Also,
Compared to a single large area diaphragm structure,
When dividing into a plurality of small diaphragms as shown in this embodiment, there is an advantage that harmonic signals other than the fundamental mode can be reduced, which also helps to reduce signal noise. Furthermore, by using the anisotropic silicon etching technique described in the explanation of FIG. It has the advantage that there are no problems at all. In addition to the embodiment shown here, there is also an embodiment (not shown) in which the area of the diaphragm 22 at the center is increased and the area of the diaphragm 22 is decreased toward the periphery.

In this case, there is an advantage that the above-mentioned directivity is further improved and a high-quality device with less noise can be provided.

FIG. 8 also shows another embodiment of the present invention. In the figure, the sixth
The same numbers as in the figures indicate the same components. In the embodiment of the present invention, the electrodes 3 formed on the upper surface of the diaphragm 22 are arranged separately for each diaphragm 22, and the aluminum wiring 60 and the contact hole 61 are arranged separately for each diaphragm 22.
It is characterized in that it is connected to the peripheral circuit 8 via. Therefore, the ultrasonic transgy having the configuration of this embodiment
In this case, it is possible to apply voltages having different intensities and phases to each diaphragm 22. In particular, by applying voltages with different phases to each diaphragm 22, the directions of ultrasonic wave transmission and reception can be changed. - It has the advantage of being able to provide services. In the embodiment shown in FIG. 8, the electrode 3 on the upper surface of the diaphragm 22 is separated for each diaphragm 22, but in addition, the electrode 3 on the upper surface of the diaphragm 22 is made common, and the second electrode 3 on the lower surface of the diaphragm 22 is separated. Even if the electrodes (not shown) are separated for each diaphragm 22, a device having the same effect as above can be realized. Furthermore, both the first electrode and the second electrode may be separated for each diaphragm 22. Although FIG. 8 shows an ultrasonic transducer array with one row and five columns, there is no need to limit the number of diaphragms 22 in any way. For example, in the 71st embodiment, if the electrodes 3 above the diaphragm 22 are arranged separately for each diaphragm 22 and each electrode is connected to the peripheral circuit 8, electric power is generated in two-dimensional directions. Kokichi is able to realize a two-dimensional ultrasonic transducer that scans the area. Furthermore, in the ultrasonic transducer array described in this embodiment, the top electrode of each diaphragm can be formed simultaneously and easily using normal IC process technology, which is a major advantage over conventional technology. .

The present invention has been described above in detail by giving examples. The configuration of the present invention is applicable regardless of whether the ultrasonic wave used as a signal changes continuously or changes in a pulsed manner with only a few wavelengths. This also holds true regardless of whether the wavelength of the ultrasound is single or multiple. Further, in the embodiment of the present invention, air is trapped in the groove under the diaphragm, but in addition to this configuration, there is also a configuration in which a hole is made in the bottom of the groove to allow air to flow. Furthermore, there are also configurations that reduce the influence of the back side of the device by placing a sound-absorbing material such as a sponge on the outside of the slot, and configurations that increase sensitivity by placing a horn on the front of the diaphragm. Included in the present invention.

In the above embodiments, the sensitivity of ultrasonic wave transmission and reception can be increased by increasing the area of the diaphragm, decreasing its thickness, or decreasing the thickness of the silicon substrate used as a spacer. It can be made delicious. However, in this case, the frequency characteristics of the device, etc. will change at the same time, so when designing an ultrasonic sensor, take the above effects into account and adjust the diaphragm to optimize the sensitivity, frequency characteristics, etc. The dimensions of the spacer must be determined.

(Effects of the Invention) As explained above, according to the present invention, it has become possible to provide a high performance, small and lightweight ultrasonic transducer. As a result, it has become possible to utilize high-performance ultrasonic transducers for detection of proximity sense and the like in fields such as industrial robots. Further, since the ultrasonic transducer of the present invention can be manufactured in large quantities using a manufacturing method that is compatible with conventional silicon IC process technology, manufacturing costs can be reduced. These effects are remarkable and the present invention is effective.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the present invention, FIG. 2 is a conceptual diagram showing the operating principle of the present invention, and FIG. 3 is a conceptual diagram showing an embodiment of a method for manufacturing the embodiment of the present invention. FIG. 4 is a cross-sectional view of a conventional ultrasonic transducer. Figure 5 is a principle diagram of a conventional electrostatic transformer, Figure 6
7 and 7 are plan views showing other embodiments of the present invention, and FIG. 8 is a plan view showing one embodiment of the ultrasonic transducer array according to the present invention. 1.31 Oxide film 2,33 Polymer film 3.4,3
．． 5.49... Electrode 5, Insulating case 6, Bonding wire 7, 38, '60... Aluminum wiring 8.3
2. Peripheral circuit 9, 30... Silicon substrate 10.1
1... Lead 12, 37, 101... Groove 13
...Gold-silicon eutectic alloy 22-diaphragm 34. , 61-Contact hole 36・Groove pattern 41...Metal case 42・
Plastic case 43...protective screen 44. ．． 45-electrode terminal 46
...Plate spring 47...Aluminum alloy plate 48.
Polyester membrane 51, mechanical element 51a, diaphragm
51b・Fixing plate 52...Electrical element 53
・Bias voltage 54...Resistance 55...
Transmitting and receiving circuits. ＼C Two strokes, I Kuni No. 3 (h) Magaken / Tan []] Gooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo 67

Claims (2)

[Claims] (1) In an electrostatic ultrasonic transducer configured with a diaphragm having a first electrode on one side of its surface and a second electrode facing the diaphragm with a spacer interposed therebetween, the diaphragm has an inorganic insulating film and An ultrasonic transducer characterized in that the spacer is constituted by a composite layer of a polymer membrane, and the spacer is constituted by silicon. (2) In an electrostatic ultrasonic transducer comprising a diaphragm having a first electrode on one side of its surface and a second electrode facing the diaphragm with a spacer interposed therebetween, the diaphragm has an inorganic insulating film and An ultrasonic transducer made of a composite layer of a polymer film and the space made of silicon is used as one element, and a plurality of said elements are arranged on the same silicon substrate, and at least one of the first or second electrode An ultrasonic transducer in which the diaphragm is separated into each element, and different voltages are applied to the diaphragm of each element.