JPH0769236B2 - Vibratory Transducer Manufacturing Method - Google Patents

Description

The present invention relates to a method of manufacturing a vibrating transducer having a vibrating beam having a shell and provided on a substrate of a silicon single crystal and made of a silicon single crystal material. is there.

More specifically, the present invention relates to a method for manufacturing a vibrating transducer having good mechanical and electrical characteristics such as low dislocation, high initial tension and high sensitivity.

<Prior Art> FIG. 4 is a structural explanatory view of a conventional example that has been generally used, showing an example of use in a pressure sensor, and FIG.
6 is a plan view with a part omitted, and FIG.

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

In these figures, 1 is a substrate made of an elastic semiconductor, 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.

The shell 5 is made of silicon in this case, and is attached to the pressure-receiving diaphragm 2 by, for example, an anodic bonding method. The shell 5 is also provided on the vibrating beam 4, but is omitted here.

The shell 5 is omitted in FIG. 4 for the sake of clarity.

FIG. 7 is an enlarged 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, and 24 is a SiO ₂ layer. A part of the epitaxial layer 22 has a gap 25 formed, for example, by under-etching.
(4) is composed of a P layer fixed at both ends and a SiO ₂ layer which straddles over the gap 25.

In FIG. 7, the P layer 23 forming the vibrating beam 3 (4) and the P layers 21a and 21b facing each other through the gap 25 form a capacitance electrode. ), P ⁺ layer 21a
By a by utilizing the electrostatic force acting between the P ⁺ layer 23 is excited, also, the electrostatic capacitance change between the P ⁺ layer 21b and the P ⁺ layer 23,
The vibration of the vibrating beam 3 (4) is detected.

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 configured as described above, if pressure is applied to the pressure receiving diaphragm 2 from the inside as shown by an arrow P in FIG. 5, 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 filed on June 26, 62, entitled "Title of Invention; Method for Manufacturing Vibration Transducer".

Hereinafter, this application will be described with reference to FIG.

In the figure, the same symbols as in FIGS. 4 to 7 indicate the same functions.

Only parts different from those in FIGS. 4 to 7 will be described below.

(1) As shown in FIG. 8 (A), n-type silicon (10
A film 101 of silicon oxide or silicon nitride is formed on the substrate 1 cut into the 0) plane. The required portions of the film 101 are removed by photolithography.

(2) Hydrogen (H ₂ ) at 1050 ℃ as shown in Fig. 8 (B)
Etching is performed with hydrochloric acid in the atmosphere to etch the required portion 102 on the substrate 1 and undercut the film 101 to form a concave portion.
Form 103.

Instead of hydrochloric acid, 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) Hydrogen (H ₂ ) at 1050 ℃ as shown in Fig. 8 (C)
The selective epitaxial growth method is carried out by mixing HCl gas as a source gas in an atmosphere.

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

A second epitaxial layer 105 corresponding to the vibrating beams 3 and 4 is selectively epitaxially grown on the surface of the first epitaxial layer 104 by using P-type silicon having a boron concentration of 10 ²⁰ cm ^-3 so as to block a required portion 102.

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

A fourth epitaxial layer 107 corresponding to the shell 5 is selectively epitaxially grown on the surface of the third epitaxial layer 106 with n-type silicon having a phosphorus concentration of 10 ¹⁷ cm ^-3 .

(4) As shown in FIG. 8 (D), a silicon oxide or silicon nitride film 101 is formed with hydrofluoric acid (HF).
And removed by etching, and an injection port 108 for the etching liquid is provided.

(5) As shown in FIG. 8 (E), a positive pulse is applied to the substrate 1 and the fourth epitaxial layer 107 with respect to the second epitaxial layer 105, and the alkaline solution is injected from the injection port 108 of the etching solution. The first epitaxial layer 104 and the third
The epitaxial layer 106 is removed by selective etching.

The difference in the 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. 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) A thermal oxidation process is performed to form a silicon oxide film 109 on each surface.

If the dimensional accuracy is looser, this step is not necessary.

(7) As shown in FIG. 8F, 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 (7) is not performed, this step is not necessary either.

(8) As shown in FIG. 8 (G), n-type silicon was epitaxially grown in hydrogen (H ₂ ) at 1050 ° C.
Then, the epitaxial growth layer 111 is formed on the outer surface of the fourth epitaxial layer 107, and the etchant injection port 108 is closed.

In this step, the etchant injection port 108 is closed by thermal oxidation.

Polysilicon is deposited on the location of the etching solution inlet 108 by the CVD method or the sputtering method, and the etching solution inlet 108 is closed.

The injection port 108 of the etching solution is filled with the silicon epitaxial method by the vacuum evaporation method.

The etchant injection port 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, 4 and the shell 5 are integrally formed, it is not necessary to join the substrate 1 and the shell 5,
The problem of instability due to joining is eliminated.

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

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

<Problems to be Solved by the Invention> However, in such a device, dislocations are generated when crystals grow and pass through the edge portion of the film 101 made of silicon oxide or the like during the epitaxial growth of the second epitaxial layer 105. Outbreak.

As a result, the tension due to the difference in impurity concentration is relaxed.

Since the crystallinity deteriorates, the leak current increases.

Since the crystallinity is poor, the breaking stress is low.

The present invention solves this problem.

It is an object of the present invention to provide a method for manufacturing a vibrating transducer having good mechanical and electrical characteristics such as low dislocation, high initial tension and high sensitivity.

<Means for Solving the Problems> In order to achieve this object, the present invention provides a silicon single crystal material which is provided on an n-type silicon single crystal substrate, is excited by an excitation means, and vibration is detected by an excitation detection means. A method of manufacturing a vibrating transducer, comprising forming a vibrating beam made of, forming a chamber with the substrate surrounding the vibrating beam, and forming a shell made of a silicon material so as to maintain a gap around the vibrating beam. A film of silicon oxide or nitride is formed on a substrate of silicon single crystal, and a required portion of the film is removed by etching, and a high concentration of a hard-to-etch portion is formed on the substrate where the vibrating beam is formed. A first diffusion layer made of P-type silicon is formed by thermal diffusion, and the film around the required portion of the film is removed by etching, and the shell side portion of the chamber and the An epitaxial layer made of n-type silicon is formed at a position where the shell is formed, and the first diffusion layer is thermally diffused to a position where a part of the chamber on the substrate side is easily etched. Forming a second diffusion layer of high-concentration P-type silicon on a portion of the first epitaxial layer where the shell-side portion of the chamber is formed, and forming a third diffusion layer of high-concentration P-type silicon that is easily etched. Are removed by etching to form an etching injection port, an etching fluid is injected from the injection port, the second and third diffusion layers are removed by selective etching, and the epitaxial layer is covered and the injection port is closed. This is a method for manufacturing a vibrating transducer characterized in that the shell is formed by selective epitaxial growth.

<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 portion corresponding to the gap by etching, it is possible to obtain a vibrating transducer in which the substrate, the vibrating beam and the shell are integrally formed.

In addition, 3 × 10 ¹⁹ is provided at the position where the vibrating beam is formed on the substrate.
Since the first diffusion layer made of P-type silicon of about / cm ³ or more is formed by thermal diffusion, there is no risk of dislocation occurring in the first diffusion layer.

Hereinafter, detailed description will be given based on examples.

<Embodiment> FIG. 1 is an explanatory view of a main part manufacturing process of an embodiment of the present invention.

In the figure, the same symbols as those in FIGS. 4 to 7 represent the same functions.

Only parts different from FIGS. 4 to 7 will be described below.

In the figure, (1) As shown in FIG. 1 (A), n-type silicon (80)
A film 201 of silicon oxide or silicon nitride is formed on the substrate 1 on the surface. The required portion 202 of the film 201 is removed by photolithography.

(2) As shown in FIG. 1 (B), the vibrating beams 3, 4 are formed on the substrate 1.
A second diffusion layer 203 made of P-type silicon having a density of 3 × 8 ¹⁹ / cm ³ or more is formed by thermal diffusion in the portion where the is formed.

(3) As shown in FIG. 1 (C), the film 2 around the location 202
Remove 01 and spread.

(4) Hydrogen (H ₂ ) at 850 ° C as shown in Fig. 1 (D)
Hydrogen chloride (HCl) gas is mixed in the source gas in the atmosphere, and n-type silicon with a phosphorus concentration of 8 ¹⁷ cm ^-3 is used to form the gap 2
The upper half of 5 and the epitaxial layer 204 corresponding to shell 5 are selectively epitaxially grown.

(5) As shown in FIG. 1 (E), heat treatment is performed to form a second diffusion layer 205 on the substrate 1 and a third diffusion layer 206 on the epitaxial layer 204 by thermal diffusion of the first diffusion layer 203.

(6) As shown in FIG. 1 (F), a silicon oxide or silicon nitride film 201 is formed into hydrofluoric acid (HF).
And removed by etching, and an injection port 207 for the etching liquid is provided.

(7) As shown in FIG. 1 (G), a positive pulse is applied to the substrate 1 and the epitaxial layer 204 with respect to the first diffusion layer 203 to inject the alkaline solution from the injection port 207 of the etching solution. Then, the second diffusion layer 205 and the third diffusion layer 206 are selectively etched and removed.

First diffusion layer 203 and second diffusion layer 205 or third diffusion layer 206
The reason why there is a difference in the etching action between and is that when the boron concentration exceeds 3 × 8 ¹⁹ cm ⁻³ , the etching action is suppressed.

(8) As shown in FIG. 1 (H), thermal oxidation is performed to form a silicon oxide film 208 on each surface.

If the dimensional accuracy is looser, this step is not necessary.

The silicon oxide film 208 on the outer surfaces of the substrate 1 and the epitaxial layer 204 is removed by the plasma etching process.

If the thermal oxidation treatment of (8) is not performed, this step is not necessary either.

(9) As shown in Fig. 1 (I), hydrogen (H ₂ ) at 850 ℃
N-type silicon is epitaxially grown in the substrate 1
Then, an epitaxial growth layer 209 is formed on the outer surface of the epitaxial layer 204, and the etchant injection port 207 is closed.

Since the vibration beams 3 and 4 and the shell 5 cannot be insulated, the vibration detection signal e is as shown in FIG. 2, e = (Zs · e ₀ ) / (Zv + Zs) Zs; Impedance e ₀ ; Electromotive force of vibrating beams 3 and 4 Zv; It becomes the internal impedance of vibrating beams 3 and 4 and decreases, but practically because Q (resonance sharpness) of vibrating beams 3 and 4 is sufficiently large. It doesn't matter.

In the above method, after the vibrating beams 3 and 4, the portion corresponding to the gap 25 and the portion corresponding to the shell 5 are formed on the substrate 1 so as to be integrated with the substrate 1, the portion corresponding to the gap 25 is removed by etching. 1 and the vibrating beams 3 and 4 and the shell 5 can be integrated into a vibrating transducer.

In addition, it is necessary to add 3 to the position where the vibrating beams 3 and 4 are formed on the substrate 1.
× 8 ¹⁹ / cm ³ of about or more first diffusion layer composed of a P-type silicon 2
Since 03 is formed by thermal diffusion, few dislocations are generated in the first diffusion layer 203.

As a result, the residual strain (tension) of the vibrating beams 3 and 4 due to the difference in impurity concentration can be kept large.

Since the crystallinity is improved, the leak current of the vibrating beams 3 and 4 is reduced.

Since the crystallinity is good, the breaking stress of the vibrating beams 3 and 4 is high.

FIG. 3 is an explanatory view of the essential parts 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 to each other. The two vibrating first oscillator 31 and the second oscillator 32 mechanically coupling the antinode portions of the vibration of the first oscillator 31 with 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, the output transformer 51 and the amplifier 52 are 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.

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 or a plurality of fixed beams.

<Effects of the Invention> As described above, the present invention forms a vibrating beam made of a silicon single crystal material, which is provided on a substrate of n-type silicon single crystal, is excited by the excitation means, and the vibration is detected by the excitation detection means. In the method of manufacturing a vibrating transducer, which surrounds the vibrating beam, forms a chamber with the substrate, and forms a shell made of a silicon material so as to maintain a gap around the vibrating beam. A film of silicon oxide or nitride is formed on the surface of the film, a required portion of the film is removed by etching, and a high-concentration P-type silicon that is difficult to be etched is formed on a portion of the substrate where the vibrating beam is formed. 1 The diffusion layer is formed by thermal diffusion, and the film around the required part of the film is removed by etching, and the shell side part of the chamber and the shell are formed. An epitaxial layer made of n-type silicon is formed in a portion of the first diffusion layer, and a first portion of high-concentration P-type silicon that is easily etched is formed in a portion where the substrate side portion of the chamber of the substrate is formed by thermal diffusion of the first diffusion layer. The second diffusion layer is formed by forming a third diffusion layer of high-concentration P-type silicon, which is easy to be etched, at a position where the shell side portion of the chamber of the first epitaxial layer is formed, and the film is removed by etching. An inlet is formed, an etching fluid is injected from the inlet, the second and third diffusion layers are removed by selective etching, and the shell is formed by selective epitaxial growth so as to cover the epitaxial layer and block the inlet. The method of manufacturing a vibrating transducer is characterized by the above.

As a result, the residual strain (tension) of the vibrating beam due to the difference in impurity concentration can be kept large.

Since the crystallinity is improved, the leak current of the vibrating beam is reduced.

Since the crystallinity is good, the breaking stress of the vibrating beam is high.

Therefore, according to the present invention, it is possible to realize a method of manufacturing a vibrating transducer having good mechanical and electrical characteristics such as low dislocation, high initial tension and high sensitivity.

[Brief description of drawings]

FIG. 1 is a process explanatory diagram of an embodiment of the present invention, FIG. 2 is an operation explanatory diagram, FIG. 3 is a use explanatory diagram, and FIGS. 4 to 7 are conventional constitutions generally used conventionally. FIG. 8 is a manufacturing process explanatory diagram 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 ... film, 202 ... location, 203 ... first diffusion layer, 204 ... epitaxial layer, 205 ... second diffusion layer,
206 ... third diffusion layer, 207 ... etching liquid inlet, 20
8 …… Silicon oxide film, 209 …… Epitaxial layer.

Front page continuation (72) Inventor Takashi Kobayashi 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. (72) Inventor Tetsuya Watanabe 2-932 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd. In-house (72) Inventor Nao Nishikawa 2-9-32 Nakamachi, Musashino-shi, Tokyo Yokogawa Electric Co., Ltd. (72) In-house Takashi Yoshida 2-9-32 Nakamachi, Musashino-shi, Tokyo Yokogawa Electric Co., Ltd. (72) Inventor Hiroshi Suzuki 2-9-32 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd.

Claims (1)

[Claims] 1. An n-type silicon single crystal substrate provided on the substrate,
Forming a vibrating beam made of a silicon single crystal material that is excited by the exciting means and the vibration is detected by the exciting detecting means, and surrounds the vibrating beam to form the chamber with the substrate so that a gap is maintained around the vibrating beam. In a method of manufacturing a vibratory transducer for forming a shell made of a silicon material, a film of silicon oxide or nitride is formed on a substrate of the silicon single crystal, and a required portion of the film is removed by etching to form a film on the substrate. A first diffusion layer made of highly-concentrated P-type silicon that is difficult to be etched is formed by thermal diffusion in a portion where the vibrating beam is formed, and the film around the required portion of the film is removed by etching; An epitaxial layer made of n-type silicon is formed on the shell side portion of the chamber and the portion where the shell is formed, and the first diffusion layer is thermally diffused to form the epitaxial layer. A second diffusion layer of high-concentration P-type silicon, which is easily etched, is formed in a portion of the substrate where the substrate side portion of the chamber is formed, and a portion of the first epitaxial layer where the shell side portion of the chamber is formed. A third diffusion layer of high-concentration P-type silicon which is easily etched, is removed by etching to form an etching injection port, and an etching fluid is injected from the injection port to form the second and third diffusion layers. A method of manufacturing a vibratory transducer, wherein the shell is removed by selective etching, and the shell is formed by selective epitaxial growth so as to cover the epitaxial layer and block the injection port.