JPH07101748B2 - Vibratory Transducer Manufacturing Method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a method for manufacturing a vibrating transducer.

More specifically, the present invention relates to a method for manufacturing a vibrating transducer having a vibrating beam made of a silicon single crystal material and provided on a silicon single crystal substrate having a shell.

<Prior Art> FIG. 10 is a structural explanatory view of a conventional example that is generally used in the past, showing an example of use in a pressure sensor, and FIG.
FIG. 12 is a cross-sectional view taken along line XX in FIG.

Such a device is disclosed, for example, in Japanese Patent Application No. 59-42632.

In these figures, 1 is a substrate made of a semiconductor having elasticity, for example, a silicon substrate is used.

Reference numeral 2 denotes a pressure-receiving diaphragm formed by utilizing a part of the semiconductor substrate 1, which is formed by etching the semiconductor substrate 1, for example.

Reference numerals 3 and 4 denote minute vibrating beams formed on the pressure-receiving diaphragm 2 and fixed at both ends. The vibrating beam 3 is located substantially at the center of the pressure-receiving diaphragm 2, and the vibrating beam 4 is located at the peripheral edge of the pressure-receiving diaphragm 2. . The vibrating beams 3 and 4 are formed, for example, by under-etching the peripheral portion of a portion corresponding to the vibrating beam in the semiconductor substrate 1, for example.

Reference numeral 5 denotes a shell, which covers the periphery of the vibrating beam 3 formed on the pressure receiving diaphragm 2 and holds the inside 25 (around the vibrating beam 3) in a vacuum state. Ciel 5
In this case, the pressure receiving diaphragm 2 is made of silicon.
Attached by, for example, an anodic bonding method. Ciel 5
Is also provided on the vibrating beam 4, but is omitted here.
The shell 5 is omitted in FIG. 10 for the sake of clarity.

FIG. 13 is an enlarged cross-sectional view showing the vibrating beam and its vicinity in FIG. Here, an example in which an n-type silicon substrate is used as the pressure receiving diaphragm 2 is shown. In this figure, 21a, 21
b is a P ⁺ layer, which is electrically separated from 21a and 21b by a notch 20. 22 is an n-type epitaxial layer, 23 is a P ⁺ layer, 24
Is a SiO ₂ layer. A part of the epitaxial layer 22 has a gap 25 formed by, for example, under-etching, and the vibrating beam 3 (4) is composed of a P layer fixed at both ends and a SiO ₂ layer which extends over the gap 25. Has been done.

In FIG. 13, the P layer 23 that constitutes the vibrating beam 3 (4) and the P layers 2a and 21b that face each other with the gap 25 in between constitute a capacitance electrode. ), P ⁺ layers 21a and P
⁺ Excited by using the electrostatic force between layer 23 and P
^The vibration of the vibrating beam 3 (4) is detected by the change in capacitance between the ⁺ layer 21b and the P ⁺ layer 23.

OSC is an oscillating circuit, which is configured externally or by using the semiconductor substrate 1. The input end is connected to the P ⁺ layer 21b, and a signal related to the vibration of the vibrating beam 3 (4) is applied. To be done. Also, the P ⁺ layer 21a is connected to the output end, and the P ⁺ layer 21a
An output signal is given between the P ⁺ layers 23. This allows the oscillator circuit
The OSC and the vibrating beam 3 (4) form a self-excited oscillation circuit that oscillates at the natural frequency of the vibrating beam.

In the pressure sensor thus configured, if pressure is applied to the pressure-receiving diaphragm 2 from the inside as shown by an arrow P in FIG. 11, the pressure-receiving diaphragm 2 is bent by the pressure and is formed in the center. A tensile force is applied to the vibrating beam 3 that is formed, and a compressive force is applied to the vibrating beam 4 that is formed on the peripheral portion of the diaphragm 2. This allows each vibrating beam
The natural frequencies f ₁ and f ₂ of 3 and 4 change differentially with respect to the pressure P. For example, the pressure P can be measured by calculating the difference f ₁ −f _2. it can.

Since the vibrating beams 3 and 4 are placed in a vacuum by the shell 5, the Q of the vibrating beams 3 and 4 can be increased.

However, in such a device, since the shell 5 has to be attached to the pressure receiving diaphragm 2, a joining technique such as an anodic joining method is required, which may adversely affect the vibrating beam during joining. In addition, there are problems such as bonding strength, and there is a limit to miniaturization.

In order to solve such a problem, the applicant of the present application
Japanese Patent Application No. 62-159073, entitled "Invention; Method for manufacturing vibrating transducer", filed on June 26, 62, is filed.

Hereinafter, this application will be described with reference to FIGS. 14 to 20.

In the figure, the same symbols as in FIGS. 10 to 13 indicate the same functions.

Only parts different from those in FIGS. 10 to 13 will be described below.

(1) As shown in FIG. 14, a silicon oxide or silicon nitride film 101 is formed on a substrate 1 cut into an n-type silicon (100) plane. The required portions of the film 101 are removed by photolithography.

(2) As shown in Fig. 15, etching was performed with hydrogen chloride in a hydrogen (H ₂ ) atmosphere at 1050 ° C, and a required portion of the substrate 1 was removed.
2 by etching, undercut the film 101,
Form 103.

Instead of hydrogen chloride, high temperature steam or oxygen may be used, or anisotropic etching with an alkali solution at 40 ° C to 130 ° C may be used.

(3) As shown in FIG. 16, a selective epitaxial growth method is performed by mixing hydrogen chloride (HCl) gas into a source gas in a hydrogen (H ₂ ) atmosphere at 1050 ° C.

That is, the first epitaxial layer 104 corresponding to the lower half of the gap 25 is selectively epitaxially grown with P-type silicon having a boron concentration of 10 ¹⁸ cm ^-3 .

With P-type silicon with a boron concentration of 10 ²⁰ cm ^-3 ,
On the surface of the epitaxial layer 104, the second epitaxial layer 105 corresponding to the vibrating beams 3 and 4 is selectively epitaxially grown so as to close the required portion 102.

The second concentration of P-type silicon with a boron concentration of 10 ¹⁸ cm ^-3
A third epitaxial layer 106 corresponding to the upper half of the gap 25 is selectively epitaxially grown on the surface of the epitaxial layer 105.

The fourth n-type silicon having a phosphorus concentration of 10 ¹⁷ cm ^-3 is formed on the surface of the third epitaxial layer 106 so as to correspond to the shell 5.
The epitaxial layer 107 is selectively epitaxially grown.

(4) As shown in FIG. 17, the silicon oxide or silicon nitride film 101 is removed by etching with hydrofluoric acid (HF), and an etching injection port 108 is provided.

(5) As shown in FIG. 18, by applying a positive pulse to the substrate 1 and the fourth layer with respect to the second layer, the injection port for the etching solution
Injecting alkaline solution from 108, the first epitaxial layer 1
04 and the third epitaxial layer 106 are selectively etched and removed.

The difference in etching action between the second epitaxial layer 105 and the first epitaxial layer 104 or the third epitaxial layer 106 is that when the boron concentration is 3 × 10 ¹⁹ cm ⁻³ or more, the etching action is suppressed and development is suppressed. It depends on what happens.

This is shown, for example, in Fig. 8 on page 123 of "Transducers '87" published by The Institute of Electrical Engineers of Japan.

(6) Thermal oxidation treatment is performed to form a silicon oxide film 109 on each surface.
Give rise to. If the dimensional accuracy is looser,
This step is not needed.

(7) As shown in FIG. 19, the silicon oxide film 109 on the outer surfaces of the substrate 1 and the fourth epitaxial layer 107 is removed by plasma etching. If the thermal oxidation treatment of (6) is not performed, this step is not necessary either.

(8) As shown in FIG. 20, n-type silicon is epitaxially grown in hydrogen (H ₂ ) at 1050 ° C. to form an epitaxial growth layer 111 on the outer surfaces of the substrate 1 and the fourth epitaxial layer 107, and the etching is performed. Close entrance 108.

In this step, the etching inlet 108 is closed by thermal oxidation.

A film of polysilicon is deposited on the portion of the etching inlet 108 by the CVD method or the sputtering method, and the etching inlet 108 is closed.

The etching injection hole 108 is filled by the silicon epitaxial method by the vacuum evaporation method.

The etching inlet 108 may be filled with an insulating material such as glass (SiO ₂ ), nitride, or alumina by the CVD method, the sputtering method, or the vapor deposition method.

As a result, (1) since the substrate 1, the vibrating beams 3 and 4 and the shell 5 are integrally formed, it is not necessary to join the substrate 1 and the shell 5, and the problem of instability due to the joining is eliminated. .

(2) With a simple structure, the external fluid and the vibrating beams 3 and 4 can be insulated, and miniaturization is easy.

(3) The position, thickness and shape of the vibrating beams 3 and 4 and the shell 5 are
It can be done easily and accurately using semiconductor process technology. Therefore, a highly accurate vibration type transducer can be obtained.

<Problems to be Solved by the Invention> However, in such an apparatus, since the n-type reactor and the p-type reactor are alternately used, the efficiency is low.

Since it moves between the n-type reactor and the p-type reactor, it is easily polluted.

The present invention solves this problem.

It is an object of the present invention to provide a method for manufacturing a vibrating transducer, which performs all epitaxial growth steps in a p-type reaction furnace except for the work of sealing an etching injection port, has a good yield, is inexpensive, and has an improved efficiency. There is.

<Means for Solving the Problem> In order to achieve this object, the present invention is provided on a substrate of a silicon single crystal, a silicon single crystal material that is excited by the excitation means and vibration is detected by the excitation detection means. In the method of manufacturing a vibrating transducer, the vibrating beam is formed, a chamber is formed around the vibrating beam, and a shell made of a silicon material is formed so as to maintain a gap around the vibrating beam. A film of silicon oxide or nitride is formed on a single crystal substrate, and a required portion of the film is removed by etching. A recess forming a part of the chamber is formed in the substrate by etching, A first epitaxial layer made of high-concentration P-type silicon which is easily etched is selectively epitaxially grown on a portion where the substrate side portion is formed, and the first epitaxial layer is formed. The second epitaxial layer made of high-concentration P-type silicon, which is difficult to be etched, is selectively epitaxially grown on a portion of the surface of the cavity layer where the vibrating beam is formed, and the portion where the shell side portion of the chamber is formed is etched. Selective epitaxial growth of a high-concentration P-type silicon of a high concentration, and a selective epitaxial growth of a fourth epitaxial layer of a high-concentration P-type silicon that covers the third epitaxial layer and is hard to be etched. An etching injection port is formed by removing it by etching, an etching fluid is injected from the injection port, the first and third epitaxial layers are removed by selective etching, and the fourth epitaxial layer is covered and the injection port is closed. The shell by selective epitaxial growth Method for manufacturing a vibration type Toransudeyusa, characterized in that form has a constitution that the adopted.

<Operation> In the above method, after the vibrating beam, the gap corresponding portion, and the shell equivalent portion are formed on the substrate so as to be integrated with the substrate,
By removing the portions corresponding to the gaps by etching, it is possible to obtain a vibrating transducer in which the substrate, the vibrating beam and the shell are integrated.

Further, all the epitaxial growth steps can be carried out in the p-type reaction furnace except the work of sealing the etching inlet.

Hereinafter, detailed description will be given based on examples.

<Embodiment> FIG. 1 is a cross-sectional perspective view of an essential part manufacturing process of an embodiment of the present invention.

In the figure, the same symbols as those in FIGS. 10 to 13 represent the same functions.

Only parts different from FIGS. 10 to 13 will be described below.

(1) As shown in FIG. 1, a silicon oxide or silicon nitride film 201 is formed on a substrate 1 cut into an n-type silicon (100) plane. The required parts of the film 201 are removed by photolithography.

(2) As shown in FIG. ₂ , the substrate 201 is etched with hydrogen chloride in a hydrogen (H ₂ ) atmosphere at 1050 ° C., the required portion 202 is etched on the substrate 1 to undercut the film 201, and the recess 203 is formed. Form.

Instead of hydrogen chloride, high temperature steam or oxygen may be used, or anisotropic etching with an alkali solution at 40 ° C to 130 ° C may be used.

(3) As shown in FIG. 3, a selective epitaxial growth method is performed by mixing HCl gas into a source gas in a hydrogen (H ₂ ) atmosphere at 1050 ° C.

That is, the first epitaxial layer 204 corresponding to the lower half of the gap 25 is selectively epitaxially grown with P-type silicon having a boron concentration of 10 ¹⁸ cm ^-3 .

Boron concentration of 3 × 10 ¹⁹ cm ^-3 P type silicon
The second epitaxial layer 2 corresponding to the vibrating beams 3 and 4 is formed on the surface of the first epitaxial layer 204 so as to cover the required portion 202.
Selective epitaxial growth of 05.

The second concentration of P-type silicon with a boron concentration of 10 ¹⁸ cm ^-3
A third epitaxial layer 206 corresponding to the upper half of the gap 25 is selectively epitaxially grown on the surface of the epitaxial layer 205.

Boron concentration of 3 × 10 ¹⁹ cm ^-3 P type silicon
A fourth epitaxial layer 207 corresponding to shell 5 is selectively epitaxially grown on the surface of the third epitaxial layer 206.

(4) As shown in FIG. 4, the silicon oxide or silicon nitride film 201 is removed by etching with hydrogen fluoride (HF), and an etching injection port 208 is provided.

(5) As shown in FIG. 5, a positive pulse is applied to the substrate 1 with respect to the fourth layer, and an alkaline solution is injected from the etching injection port 208 to form the first epitaxial layer 204 and the third epitaxial layer 206. Are selectively etched and removed.

The difference in the etching action between the second epitaxial layer 205 and the first epitaxial layer 204 or the third epitaxial layer 206 is that when the boron concentration is 3 × 10 ¹⁹ cm ⁻³ or more, the etching action is suppressed. It depends on what happens.

(6) A silicon oxide film 209 is formed on each surface by thermal oxidation.
Give rise to. If the dimensional accuracy is looser,
This step is not needed.

(7) As shown in FIG. 6, the silicon oxide film 209 on the outer surfaces of the substrate 1 and the fourth epitaxial layer 207 is removed by plasma etching. If the thermal oxidation treatment of (6) is not performed, this step is not necessary either.

(8) As shown in FIG. 7, n-type silicon is epitaxially grown in hydrogen (H ₂ ) at 1050 ° C. to form an epitaxial growth layer 211 on the outer surfaces of the substrate 1 and the fourth epitaxial layer 207, and etching is performed. Close entrance 208.

In this step, the etching injection port 208 is closed by thermal oxidation.

Polysilicon is deposited on the portion of the etching inlet 208 by the CVD method or the sputtering method, and the etching inlet 208 is closed.

The etching injection port 208 is filled with the silicon epitaxial method by the vacuum evaporation method.

The etching injection port 208 may be filled with an insulating material such as glass (SiO ₂ ), nitride, or alumina by the CVD method, the sputtering method, or the vapor deposition method.

Since the vibration beams 3 and 4 and the shell 5 cannot be insulated, the vibration detection signal e is as shown in FIG. 8, e = (Zs · e _o ) / (Zv + Zs) Zs; Impedance e _o ; electromotive force of the vibrating beams 3 and 4 Zv; it becomes the internal impedance of the vibrating beams 3 and 4 and decreases, but since the Q (resonance sharpness) of the vibrating beams 3 and 4 is sufficiently large, it is practically used. It doesn't matter.

As a result, (1) since the substrate 1, the vibrating beams 3 and 4 and the shell 5 are integrally formed, it is not necessary to join the substrate 1 and the shell 5, and the problem of instability due to the joining is eliminated. .

(2) With a simple structure, the external fluid and the vibrating beams 3 and 4 can be insulated, and miniaturization is easy.

(3) The position, thickness and shape of the vibrating beams 3 and 4 and the shell 5 are
It can be done easily and accurately using semiconductor process technology. Therefore, a highly accurate vibration type transducer can be obtained.

(4) Except for the sealing work of the etching injection port 208, all the epitaxial growth steps can be performed in the p-type reaction furnace, so that a vibrating transducer that is less likely to be contaminated, has a good yield, is inexpensive, and has improved efficiency is provided. can get.

In addition, in the above-mentioned embodiment, the example applied to the pressure sensor has been described, but the present invention is not limited to this and may be applied to, for example, a temperature sensor and an acceleration sensor.

Further, the above-described manufacturing method can be applied not only to the vibrating beams 3 and 4 fixed at both ends but also to a cantilever beam or a plurality of fixed beams.

FIG. 9 is an explanatory view of the essential configuration of an example of use of a vibrating beam manufactured by the apparatus of the present invention.

In the figure, 3 is a vibrating beam. The vibrating beam 3 has two ends fixed to the diaphragm 2 and arranged in parallel with each other. The first vibrating element 31 and the second vibrating element 32 mechanically couple the antinode portions of the vibration of the first vibrating element 31 to each other. With.

40 is a direct current magnetic field orthogonal to the vibrating beam 3 is applied by the magnet 13 and an alternating current is applied to both ends of one of the first oscillators 31 by an input transformer 41 to move the vibrating beam 3 in a direction orthogonal to the magnetic field and the current by a magnetic induction action. It is an exciting means for exciting.

The secondary side of the input transformer 41 is connected to both ends of the one first oscillator 31.

50 is a vibration detecting means for detecting an electromotive force generated at both ends of the other first vibrator 31. In this case, output transformer 5
1, the amplifier 52 is used. The primary side of the output transformer 51 is connected to both ends of the other first oscillator 31, the secondary side is connected to the output terminal 53 via the amplifier 52, and is branched and connected to the primary side of the input transformer 41. As a whole, a positive feedback self-excited oscillation circuit is formed. The vibration of the vibrating beam 3 is detected by the vibration detecting means 50 and taken out as an output signal.

<Effects of the Invention> As described above, the present invention provides a vibrating beam made of a silicon single crystal material, which is provided on a substrate of a silicon single crystal, is excited by an excitation unit, and vibration is detected by an excitation detection unit, In a method for manufacturing a start-up type transducer, which encloses the vibrating beam, forms a chamber with the substrate, and forms a shell made of a silicon material so that a gap is maintained around the vibrating beam, a silicon is formed on the silicon single crystal substrate. A film of oxide or nitride is formed, and a required portion of the film is removed by etching. A recess forming a part of the chamber is formed by etching in the substrate, and a substrate side part of the chamber is formed. Selectively epitaxially grow a first epitaxial layer made of high-concentration P-type silicon, which is easily etched, on the surface of the first epitaxial layer. A second epitaxial layer made of high-concentration P-type silicon, which is difficult to be etched, is selectively epitaxially grown on the portion where the beam is formed, and high-concentration P-type silicon that is easily etched on the portion where the shell side portion of the chamber is formed. Selectively epitaxially growing a third epitaxial layer made of Pd, and selectively epitaxially growing a fourth epitaxial layer that covers the third epitaxial layer and is made of high-concentration P-type silicon that is difficult to be etched. Forming a shell by selectively injecting an etching fluid from the injection port to remove the first and third epitaxial layers by selective etching, covering the fourth epitaxial layer and closing the injection port. Characterized by That it was adopted a method of manufacturing a vibration-type Toransudeyusa.

As a result, (1) since the substrate, the vibrating beam and the shell are integrally formed, it is not necessary to bond the substrate and the shell, and the problem of instability due to the bonding is eliminated.

(2) With a simple structure, the external fluid and the vibrating beam can be insulated, and miniaturization can be facilitated.

(3) The position, thickness, and shape of the vibrating beam or shell can be easily and accurately made using semiconductor process technology.

Therefore, a highly accurate vibration type transistor can be obtained.

(4) Except for the work of sealing the etching inlet, all the epitaxial growth steps can be performed in the p-type reaction furnace, so that it is possible to obtain a vibrating transducer that is less likely to be contaminated, has a high yield, and has improved efficiency.

Therefore, according to the present invention, all the epitaxial growth steps, except the sealing work of the etching inlet, are performed in the p-type reaction furnace, and the manufacturing method of the vibrating transducer with good yield, low cost, and improved efficiency. Can be realized.

[Brief description of drawings]

FIGS. 1 to 7 are process explanatory diagrams of an embodiment of the present invention, FIG. 8 is an operational explanatory diagram, 9 o'clock is a usage explanatory diagram, and FIGS. 10 to 13 are generally used conventionally. FIG. 14 to FIG. 20 are diagrams for explaining the construction of the conventional example, and FIGS. 14 to 20 are explanatory diagrams of the manufacturing process of Japanese Patent Application No. 62-159073, “Title of Invention: Manufacturing Method of Vibratory Transducer”. 1 ... Substrate, 13 ... Magnet, 2 ... Pressure receiving diaphragm, 3,
4 …… Vibration beam, 20 …… notch, 21a, 21b, 23 …… P ⁺ layer, 2
2 ... n-type epitaxial layer, 24 ... SiO ₂ , 25 ... gap, 31 ... first oscillator, 32 ... second oscillator, 40 ... excitation means, 41 ... input transformer, 42 ... … Input terminal, 50 …… Vibration detection means, 51 …… Output transformer, 52 …… Amplifier, 53…
… Output terminal, 201 …… membrane, 202 …… location, 203 …… recess, 2
04 …… first epitaxial layer, 205 …… second epitaxial layer, 206 …… third epitaxial layer, 207 …… fourth epitaxial layer, 208 …… etching inlet, 209 …… silicon oxide film, 211 …… epitaxial layer.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Takashi Kobayashi 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) Tetsuya Watanabe 2-39 Nakamachi, Musashino City, Tokyo Yoko Inside the Kawa Denki Co., Ltd. (72) Inventor Nao Nishikawa 2-9-32 Nakamachi, Musashino-shi, Tokyo Inside Yokogawa Electric Co., Ltd. (72) Takashi Yoshida 2-9-32 Nakamachi, Musashino-shi, Tokyo Yokogawa Electric Within the corporation (56) Reference JP-A-60-186725 (JP, A) JP-A-3-204978 (JP, A) JP-B 6-28320 (JP, B2)

Claims (1)

[Claims] 1. A vibrating beam made of a silicon single crystal material which is provided on a silicon single crystal substrate and which is excited by an exciting means and whose vibration is detected by an excitation detecting means is formed, and the vibrating beam is surrounded by the substrate and the chamber. And forming a shell made of a silicon material so that a gap is maintained around the vibrating beam, wherein a silicon oxide or nitride film is formed on the silicon single crystal substrate. Then, a required portion of the film is removed by etching, a recess forming a part of the chamber is formed in the substrate by etching, and a high concentration P that is easily etched in a portion of the chamber where the substrate side portion is formed. The first epitaxial layer made of silicon-shaped silicon is selectively epitaxially grown, and the first epitaxial layer is formed on the surface of the first epitaxial layer at a position where the vibrating beam is formed. Selectively epitaxially grow a second epitaxial layer of high concentration P-type silicon which is difficult to be etched, and selectively epitaxially grow a third epitaxial layer of high concentration P-type silicon which is easily etched in a portion where the shell side portion of the chamber is formed. Then, a fourth epitaxial layer which covers the third epitaxial layer and is made of high-concentration P-type silicon that is difficult to be etched is selectively epitaxially grown, and the film is removed by etching to form an etching injection port. And the first and third epitaxial layers are removed by selective etching, and the shell is formed by selective epitaxial growth so as to cover the fourth epitaxial layer and block the injection port. How to make .