JPH05292598A - Sound wave transducer - Google Patents

Abstract

PURPOSE:To reduce the overall size of the sound wave transducer while maintaining its precise shape and to improve the directivity of an ultrasonic wave and improve the sensitivity. CONSTITUTION:A thin film type substrate part 3 is formed on the other end surface 1B of a pedestal 1 formed of a silicone material in a prismatic shape by using an oxidizing method, and the vibrator 4 consisting of electrodes 5 and 7 and a piezoelectric body 6 is provided on the top surface of the substrate part 3. A horn 8 formed of a silicone material in a prismatic shape in another process and the pedestal 1 are joined together by anode connection to manufacture the sound wave transducer. When a voltage signal is applied to the vibrator 4 through the electrodes 5 and 7, the vibrator 4 finely vibrates in opening parts 2 and 9 to generate an ultrasonic wave, which is increased in directivity by the horn 8 and sent out to an external body. A reflected wave from the body is collected by the horn 8 and sent to the vibrator 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound wave transducer suitable for use in, for example, an ultrasonic sensor for detecting the presence or absence of an object and the distance to the object.

[0002]

2. Description of the Related Art Generally, an ultrasonic sensor used for detecting passage (presence / absence detection) of an object such as a product, distance measurement, shape measurement, etc. converts mechanical vibration due to sound pressure and electric signal to each other. A sound wave transducer is provided, and the presence or absence of an object or the like is detected in a non-contact manner by receiving a reflected wave from the object while emitting ultrasonic waves to the object by the sound wave transducer.

As such an acoustic wave transducer, a pedestal made of a metal material, a vibrator provided on the pedestal and having electrodes on both surfaces of a piezoelectric body, and a vibrator provided so as to cover the vibrator. It is known that it is composed of a metal horn.

[0004]

By the way, since the above-described sound wave transducer according to the prior art is provided with a metal horn, the directivity of the ultrasonic wave generated by the vibrator is enhanced by the metal horn. , The sensitivity can be improved. However, since this horn is made of a metal material and is formed into a shape that opens at a predetermined angle, it is difficult to reduce the size of the horn while maintaining its precise shape. There is a problem that the manufacturing cost is significantly reduced and the manufacturing cost is increased.

For this reason, in the above-mentioned conventional technique, the acoustic wave transducer cannot be downsized because of the metal horn, no matter how small the vibrator itself including the piezoelectric element or the like is downsized. There is a problem that the degree and usability are low. Particularly, in a one-dimensional array type or two-dimensional array type sound wave transducer used for detecting multiple points on an object surface, a plurality of transducers are arranged linearly or in a plane. Therefore, if a metal horn is provided for each vibrator, the overall size becomes large, and there is a problem in that the degree of freedom in mounting is greatly reduced.

On the other hand, in order to solve the above problems, there is also known a sound wave transducer in which a horn made of metal is omitted and a vibrator is provided on a pedestal made of a silicon material. In this case, a semiconductor such as photolithography is used. The miniaturization of the acoustic wave transducer can be achieved by using the fine processing technology. However, if this acoustic wave transducer is miniaturized, the size of the oscillator also becomes smaller and the transmission output of the ultrasonic wave emitted from the oscillator becomes weaker. Therefore, the reach distance of the ultrasonic wave becomes shorter and the performance is significantly reduced. There is. Further, since the horn is omitted for downsizing, there is a problem that the directivity of ultrasonic waves is low, and the detection accuracy and reliability are low.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to reduce the overall size while maintaining a precise shape and to improve the directivity of ultrasonic waves to improve the sensitivity. An object is to provide a sound wave transducer.

[0008]

In order to solve the above-mentioned problems, the structure adopted by the present invention is a pedestal made of silicon provided with an opening portion whose diameter is successively reduced from one end side to the other end side, A flat plate-shaped substrate portion provided on the other end side of the pedestal so as to cover the opening, a first electrode provided on the other end side of the substrate portion, and a first electrode other than the first electrode. A piezoelectric body provided on the end side, and a second electrode provided on the other end side of the piezoelectric body,
Provided on the pedestal at the other end of the second electrode,
The horn is made of silicon and has an opening that is gradually expanded from one end to the other end.

[0009]

Since the pedestal and the horn are made of a silicon material, semiconductor microfabrication technology can be used to reduce the overall size of the acoustic wave transducer. And
This silicon horn can enhance the directivity of the sound wave generated by the vibration of the piezoelectric body.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.

In the figure, 1 is about 30 from a silicon material.
1 shows a pedestal formed in the shape of a rectangular tube having a thickness dimension h1 of about 0 μm, and at the center of the pedestal 1, there is a tapered opening 2 whose diameter gradually decreases from one end face 1A to the other end face 1B. It is formed in the axial direction. Further, on one end surface 1A of the pedestal 1 or the like, an oscillation circuit for supplying a voltage signal to the vibrator 4 described later, a receiving circuit for processing the voltage signal from the vibrator 4 (neither shown), etc. are patterned. Has been formed. here,
The opening 2 is about 55 ° which is determined by the physical properties of silicon by using the anisotropic etching technique of silicon.
Is formed in a taper shape that is inclined at an angle α 1. The opening 2 facilitates the vibration of the vibrator 4.

Reference numeral 3 denotes a substrate portion integrally formed on the other end surface 1B of the pedestal 1 and made of silicon dioxide. As shown in FIG. 2, the substrate portion 3 is provided with means such as a CVD method and a thermal oxidation method. A film of silicon dioxide having a thickness of about 0.5 to 1 μm is formed on the other end surface 1B side of the pedestal 1, and unnecessary portions are etched to form a rectangular thin plate-like film. The lead portions 3A and 3A corresponding to the lead portions 5A and 7A of the electrodes 5 and 7 are integrally formed.
A and 7A are electrically insulated from the pedestal 1. And
Since the substrate portion 3 is formed in a thin plate shape, it has flexibility and vibrates together with the vibrator 4.

Reference numeral 4 denotes a vibrator which is located in a housing hole 10 described later and is provided on the other end side of the substrate portion 3. The vibrator 4 is
The first electrode 5 which is provided on the other end side of the substrate portion 3 using a means such as vapor deposition or sputtering and which is formed in a substantially rectangular shape and has a lead portion 5A from a metal material such as aluminum, and the first electrode. 5, which is provided on the other end side of the piezoelectric element 5 by means such as a CVD method or a sputtering method, and is formed into a rectangular thin film from a piezoelectric material such as zinc oxide (ZnO); and the other end side of the piezoelectric element 6. And a second electrode 7 which is provided in the same manner as the first electrode using a means such as vapor deposition and is formed in a substantially rectangular shape having a lead portion 7A from a metal material such as aluminum. There is. Here, each of the electrodes 5 and 7 is formed to have a thickness dimension of, for example, about 0.3 to 0.5 μm and slightly smaller than that of the piezoelectric body 6, and the piezoelectric body 6 has a thickness of about 2 to 20 μm. Formed so as to have a sizing dimension.

When a voltage signal is applied through the electrodes 5 and 7, the vibrator 4 vibrates in the axial direction (vertical direction in FIG. 1) and generates ultrasonic waves according to the voltage signal. In addition, when a reflected wave reflected by an external object is received, it vibrates in the axial direction and outputs a voltage signal corresponding to this reflected wave.

Numeral 8 is located on the other end side of the vibrator 4 and is fixed on the other end surface 1B of the pedestal 1, and as shown in FIG. A horn formed in a cylindrical shape is shown, and the horn 8 is
As shown in FIG. 4, the one end surface 8A is the other end surface 1B of the pedestal 1.
And is fixed directly to the pedestal 1 by means of anodic bonding technology or the like. The horn 8 has an opening 9 located at the center of the horn 8 corresponding to the opening 2 of the pedestal 1 and having a diameter gradually increasing from one end face 8A to the other end face 8B.
Is formed, and an angular accommodation hole 10 extending outward is integrally formed on one end 9A side of the opening 9. Then, the vibrator 4 is housed in the housing hole 10, so that the periphery of the vibrator 4 is sandwiched between the base 1 and the horn 8.

Here, the opening 9 is the pedestal 1 described above.
The opening 2 is formed in a taper shape inclined by an angle α 2 of about 55 ° by means of an anisotropic silicon etching technique or the like. And the horn 8
Is to send the ultrasonic waves generated by the oscillator 4 to the outside with high directivity, collect the reflected waves reflected by an external object, and transmit them to the oscillator 4.

The sound wave transducer according to this embodiment has the above-mentioned structure. Next, a method of manufacturing the sound wave transducer will be described with reference to FIGS.

First, in the substrate portion forming step shown in FIG. 5, a film is formed on the surface of the pedestal member 11 formed of a silicon material in a prismatic shape having a thickness dimension h1 by means of a CVD method, a thermal oxidation method or the like. After integrally forming a rectangular thin plate-like substrate portion 3 having a thickness of 0.5 to 1 μm, as shown in FIGS. 2 and 4, the outer peripheral side is cut off by etching so as to leave each lead portion 3A, and a horn is formed. A joint surface for joining 8 and the pedestal 1 is secured.

Next, in the first electrode forming step shown in FIG. 6, 0.3 to 0.5 μm is formed on the surface of the substrate portion 3 formed in the substrate portion forming step by means such as vapor deposition and sputtering.
The first electrode 5 made of aluminum and having a thickness of about m is formed.

Then, in the piezoelectric body forming step shown in FIG.
On the surface of the first electrode 5, a rectangular thin-film piezoelectric body 6 made of a piezoelectric material such as zinc oxide (ZnO) having a thickness of about 2 to 20 μm is formed on the surface of the first electrode 5 by means of CVD or sputtering. To do.

Next, in the second electrode forming step shown in FIG. 8, a method such as vapor deposition or sputtering is used to form 0.3 on the surface of the piezoelectric body 6 in the same manner as in the first electrode forming step. ~
A second electrode 7 made of aluminum having a thickness of about 0.5 μm is formed. As a result, the electrodes 5 and 7 are formed on both surfaces of the piezoelectric body 6, and the vibrator 4 is completed.

Then, in the pedestal forming step shown in FIG. 9, the pedestal member 11 is formed by using the anisotropic silicon etching technique.
A tapered opening 2 is formed in the central part of the taper 1 so that the diameter thereof is gradually reduced toward the substrate part 3, whereby the pedestal 1 is formed. Here, the angle α1 at which the opening 2 is inclined is a value determined by the physical properties of silicon and is about 55 °.

Finally, in the joining step shown in FIG. 10, the horn 8 and the pedestal 1 provided with the vibrator 4 which are formed in another step by the silicon anisotropic etching technique are joined by the anodic joining technique. , Complete the sonic transducer.

The acoustic wave transducer according to this embodiment is
It is manufactured in this way, and when a voltage signal is applied to the vibrator 4 via the electrodes 5 and 7, the vibrator 4 moves in the openings 2 and 9 together with the substrate 3 in the axial direction. It vibrates and generates ultrasonic waves according to this voltage signal. Then, the ultrasonic waves are emitted (transmitted) toward an external object while the directivity is enhanced by the horn 8, reflected by the object, collected by the horn 8 and transmitted to the vibrator 4. As a result, the vibrator 4 vibrates slightly and outputs a voltage signal corresponding to the reflected wave to the outside through the electrodes 5 and 7.

Thus, according to this embodiment, the pedestal 1 and the horn 8 are respectively formed from a silicon material by using the anisotropic etching technique of silicon, and the two are bonded by using a bonding means such as anodic bonding. Therefore, the sound wave transducer as a whole can be surely downsized, and can be formed into a precise shape. In particular, since the pedestal 1 and the horn 8 are formed by using the anisotropic silicon etching technique, the angles α 1 and α 2 of the openings 2 and 9 can be uniquely determined based on the physical properties of silicon. Therefore, the openings 2 and 9 can be precisely formed.

As a result, the directivity of the ultrasonic wave from the vibrator 4 can be effectively enhanced by the silicon horn 8, and the detection sensitivity and performance can be greatly improved, and the flexibility of mounting and usability can be improved. Can be improved. In particular, when forming a one-dimensional array type or two-dimensional array type acoustic wave transducer, a large number of transducers can be provided in a small area, so the measurement accuracy of the surface roughness and shape of the object is greatly improved. can do.

Further, since the pedestal 1 is made of a silicon material, circuits such as an oscillation circuit, a receiving circuit and a temperature compensating circuit can be easily formed on the pedestal 1 by patterning, so that the circuit can be integrated. You can Furthermore, since the silicon material is easily microfabricated and has excellent mass productivity, the manufacturing cost can be significantly reduced.

In the above embodiment, the sound wave transducer in which the single vibrator 4 is provided on the pedestal 1 has been exemplified, but the present invention is not limited to this, and the pedestal 1 on the pedestal 1 is modified as shown in FIG. 11, for example. May be arranged in a linear shape or a plane shape to form a one-dimensional array type or two-dimensional array type acoustic wave transducer. In this case,
Openings 2 and 9 corresponding to each transducer 4 on the horn 8 and the pedestal 1
May be formed respectively.

In the above embodiment, the base 1 and the horn 8 are
However, the present invention is not limited to this, and may be formed into another shape such as a cylindrical shape by using a means such as an ion beam etching technique.

Furthermore, in the above-mentioned embodiment, the piezoelectric body 6 is described as being formed of a piezoelectric material such as zinc oxide, but the present invention is not limited to this, and for example, a thin film of another inorganic piezoelectric material such as PZT or lead titanate, or the like. It may be formed using a thin piece of ceramic bulk or an organic piezoelectric material such as polyvinylidene fluoride (PVDF). Further, a protective layer may be provided on the other surface side of the second electrode 7.

Furthermore, in the above embodiment, the substrate portion 3 is formed as a silicon dioxide film by partially oxidizing the surface of the pedestal 1 made of silicon by means of a CVD method, a thermal oxidation method or the like. However, instead of this, for example, CVD
Nitrogen may be added to the pedestal 1 by the method to form a nitride film, or the nitride film, the silicon dioxide film,
You may form as a multilayer film which laminated | stacked the silicon film in arbitrary combinations.

[0032]

As described above in detail, according to the present invention, a silicon pedestal provided with an opening whose diameter is sequentially reduced from one end to the other end, and the opening is covered. A flat plate-shaped substrate portion provided on the other end side of the pedestal, a first electrode provided on the other end side of the substrate portion, and a piezoelectric body provided on the other end side of the first electrode A second electrode provided on the other end side of the piezoelectric body, a second electrode provided on the pedestal located on the other end side of the second electrode, and the diameter gradually increased from one end side to the other end side. Since it is composed of a silicon horn having an opening formed therein, it is possible to surely reduce the size of the entire acoustic wave transducer by using a semiconductor fine processing technique. As a result, the directivity of the sound wave generated by the piezoelectric body can be effectively increased by the silicon horn, the detection sensitivity and the performance can be improved, and the mounting flexibility and usability can be improved. ..

In particular, in the case of a one-dimensional array type or two-dimensional array type acoustic wave transducer in which a plurality of piezoelectric bodies are arranged, it is possible to improve the measurement accuracy of the roughness or shape of the object surface. Further, since the pedestal is made of a silicon material, circuits such as an oscillation circuit, a receiving circuit, and a temperature compensation circuit can be easily patterned on the pedestal, and the circuit can be integrated. Further, since the silicon material is easily microfabricated and has excellent mass productivity, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a sound wave transducer according to an embodiment of the present invention.

FIG. 2 is a plan view showing the sound wave transducer in FIG. 1 with a horn removed.

FIG. 3 is a plan view of a horn.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a vertical cross-sectional view showing a substrate portion forming step.

FIG. 6 is a vertical sectional view showing a first electrode forming step.

FIG. 7 is a vertical sectional view showing a piezoelectric body forming step.

FIG. 8 is a vertical sectional view showing a second electrode forming step.

FIG. 9 is a vertical sectional view showing a pedestal forming step.

FIG. 10 is a vertical cross-sectional view showing a joining step of joining a pedestal and a horn.

FIG. 11 is a plan view showing a modified example of this embodiment.

[Explanation of symbols]

 1 pedestal 2 opening part 3 substrate part 5 first electrode 6 piezoelectric body 7 second electrode 8 horn 9 opening part

Claims (1)

[Claims] 1. A pedestal made of silicon provided with an opening whose diameter is sequentially reduced from one end to the other end, and a flat plate provided on the other end of the pedestal so as to cover the opening. Shaped substrate portion, a first electrode provided on the other end side of the substrate portion,
A piezoelectric body provided on the other end side of the first electrode, a second electrode provided on the other end side of the piezoelectric body, and a pedestal located on the other end side of the second electrode. A sound wave transducer comprising: a silicon horn provided with an opening whose diameter gradually increases from one end side to the other end side.