JPH02103432A - Manufacture of oscillation type transducer - Google Patents

Abstract

PURPOSE:To increase initial tension and to improve sensitivity by forming a vibration beam, a gap corresponding part and a shell corresponding part on a substrate so as to form a unitary body, and thereafter etching and removing the gap corresponding part. CONSTITUTION:A silicon oxide film 201 is formed on a substrate 1 having an n-type silicon surface. A required part 202 is removed to form a first diffused layer 203 comprising p-type silicon at a position where a vibration beam is formed on said substrate 1. Then, an epitaxial layer 204 is selectively grown. Thereafter, a second diffused layer 205 is formed on the substrate 1 by the thermal diffusion of the layer 203. A third diffused layer 206 is formed on the layer 204. The film 201 is etched away to provide an etching liquid injecting port 207. Alkali liquid is injected through the injecting port 207. The layers 205 and 206 are removed to form a silicon oxide film 208 is formed on each surface. The film 208 at the outer surfaces of the substrate 1 and the layer 204 are removed by plasma etching. Then n-type silicon is epitaxially grown, and the injecting port 207 is closed by an epitaxially grown film 209.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a vibrating transducer having a shell, a vibrating beam made of a silicon single crystal material, and provided on a silicon single crystal substrate. be.

More specifically, the present invention relates to a method for manufacturing a vibrating transducer that has good mechanical and electrical properties such as few dislocations, large initial tension, and high sensitivity.

<Prior art> Fig. 4 is an explanatory diagram of the configuration of a conventional example commonly used in the past, showing an example of use in a pressure sensor.
The XX sectional view in the figure and FIG. 6 are partially omitted plan views.

Such a device is shown, for example, in 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 constructed using a part of the semiconductor substrate 1, for example, by etching the semiconductor substrate 1.

3 and 4 are minute vibrating beams formed on the pressure receiving diaphragm 2 and fixed at both ends.

The vibrating beam 3 is located approximately at the center of the pressure receiving diaphragm 2, and the vibrating beam 4 is located at the periphery of the pressure receiving diaphragm 2.

The vibrating beam 3.4 is formed by, for example, under-etching the peripheral portion of the semiconductor substrate 1 corresponding to the vibrating beam.

Reference numeral 5 denotes a shell that covers the periphery of the vibrating beam 3 formed on the pressure receiving diaphragm 2 and maintains the interior 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, anodic bonding. Although the shell 5 is also provided on the vibrating beam 4, it is omitted here.

Note that the shell 5 is omitted in FIG. 4 for clarity.

FIG. 7 is an enlarged sectional view showing the vicinity of the vibrating beam in FIG. 5. Here, an example is shown in which an n-type silicon substrate is used as the pressure receiving diaphragm 2. In this figure, 21a
, 21b is the 21st layer, and 21a and 21b are the notches 20.
electrically isolated by

22 is an n-type epitaxial layer, 23 is a P multilayer, 24 is an S
i02 layer. A part of the epitaxial layer 22 is
For example, a gap 25 is formed by under-etching, and the vibrating beam 3 (4) is composed of a P layer and a 5102 layer that are fixed at both ends and span the gap 25.

In FIG. 7, two layers 23 forming the vibrating beam 3 (4),
Two layers 21a facing each other with a gap 25 in between.

21b constitutes a capacitance electrode, in which the vibrating piece 3 (4) is excited using the electrostatic force acting between the P layer 21a and the P"M23, and the P layer 21b and Due to the capacitance change between the P layer 23 and the vibrating beam 3 (4)
It is designed to detect vibrations.

O20 is an oscillation circuit, and this circuit is configured externally or using the semiconductor substrate 1, and the input terminal is connected to the P layer 2.
1b is connected, and a signal related to the vibration of the vibrating beam 3 (4) is applied. Further, the output end is connected to the P layer 21a, and provides an output signal between the P layer 21a and the P+ layer 3. As a result, the oscillation circuit O8C and the vibrating beam 3 (4) constitute an automatic oscillation circuit that oscillates at the natural frequency of the vibrating beam.

In the pressure sensor configured in this way, if pressure is applied to the pressure receiving diaphragm 2 from the inside as shown by the arrow P in FIG. A tensile force is applied to the vibrating beam 3 formed on the diaphragm 2, and a compressive force is applied to the vibrating beam 4 formed at the peripheral edge of the diaphragm 2. As a result, the natural frequencies ft and f2 of each vibrating beam 3 and 4 change differentially with respect to the pressure P. For example, the pressure P can be measured by calculating the difference between f and -f2. be able to.

Since the vibrating beams 3 and 4 are placed in a vacuum by the shell 5, the Q of the vibrating beams 3.4 can be increased.

However, in such a device, since the shell 5 must be attached to the pressure-receiving diaphragm 2, a bonding technique such as an anodic bonding method is required, and there is a risk that the vibration beam will be adversely affected during bonding. Further, problems such as bonding strength arise, and there is a limit to miniaturization.

In order to solve these problems, the applicant of the present application has filed Japanese Patent Application No. 159073/1982 filed on June 26, 1988.
The title of the invention is ``Method for manufacturing a vibrating transducer''.

This application will be explained below with reference to FIG.

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

Hereinafter, only the differences from FIGS. 4 to 7 will be explained.

(1) As shown in Figure 8(A), n-type silicon (10
0) A film 101 of silicon oxide or silicon nitride is formed on the substrate 1 which has been cut into a plane. 119101
Required portions of are removed by photolithography.

(2) As shown in Figure 8 (B), hydrogen (
H2) Etching is performed with hydrochloric acid in an atmosphere to etch required portions 102 on the substrate 1 to undercut the film 101 and form recesses 103.

Note that instead of hydrochloric acid, high-temperature steam or oxygen may be used, or anisotropic etching may be performed using an alkaline solution at a temperature of 40 DEG C. to 130 DEG C.

(3) As shown in Figure 8 (C), hydrogen (
H2) Selective epitaxial growth is performed in an atmosphere by mixing MCI gas into the source gas.

In other words, ■P-type silicon with a boron concentration of 10"cm"2,
First epitaxial layer 1 corresponding to the lower half of the gap 25
04 is selectively epitaxially grown.

■ P-type silicon with a boron concentration of 10"cm"3,
At a required location 10 on the surface of the first epitaxial layer 104
A second epitaxial layer 105 corresponding to the vibrating beams 3 and 4 is selectively grown epitaxially so as to cover the vibrating beams 3 and 4.

(2) 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 with a boron concentration of 10 cm'.

■By using n-type silicon with a phosphorus concentration of 1017 cm-2,
A fourth epitaxial layer 107 corresponding to the shell 5 is selectively epitaxially grown on the surface of the third epitaxial layer 106 .

(4) As shown in FIG. 8CD), silicon oxide or silicon nitride 119101 is removed by etching with hydrofluoric acid (HF), and an etching solution injection port 108 is provided.

(5) As shown in FIG. 8(E), the substrate 1 and the fourth epitaxial layer 10 are
7, a positive pulse is applied to the etching solution inlet 10.
8, the alkaline solution is injected into the first epitaxial layer 1.
04 and the third epitaxial layer 106 are selectively etched and removed.

Second epitaxial layer 105 and first epitaxial layer 1
The reason for the difference in etching effect between the etching effect and the third epitaxial layer 1°6 is that the boron concentration is 3×101.
This is because when the value exceeds "gcm-", the etching action is suppressed.

This is shown, for example, in Fig. 8 of [Transducer Zoo 87] published by the Institute of Electrical Engineers of Japan, page 123.

(6) Perform thermal oxidation treatment to form a silicon oxide film 109 on each surface.
give rise to

Note that this step is not necessary if the dimensional accuracy is less strict.

(7) As shown in FIG. 8(F), the silicon oxide film 109 on the outer surfaces of the substrate 1 and the fourth epitaxial layer 107 is removed by plasma etching. Furthermore, (7)
This step is also not necessary if the thermal oxidation treatment is not performed.

(8) Figure 8 (G) 4: As shown, 1050”C (7)
Epitaxial growth of n-type silicon is performed in hydrogen (H2) to form an epitaxial growth layer 111 on the outer surfaces of the substrate 1 and the fourth epitaxial layer 107, and the injection port 108 for the etching solution is closed.

Note that this process is (2) Close the etching solution injection port 108 by thermal oxidation.

(2) A film of polysilicon is deposited on the etching solution injection port 108 by CVD or sputtering, and the etching solution injection port 108 is closed.

(2) Filling the etching solution injection port 108 by silicon epitaxial method using vacuum evaporation method.

(2) The etching solution injection port 108 may be filled with an insulator such as glass (Si02), nitride, alumina, etc. by CVD, sputtering, or vapor deposition.

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 bond the substrate 1 and the shell 5, and the problem of instability due to bonding is eliminated. .

(2) With a simple structure, the vibration beam 3.4 can be insulated from the external fluid and can be easily miniaturized.

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

<Problems to be Solved by the Invention> However, in such an apparatus, during the epitaxial growth of the second epitaxial layer 105, dislocations occur when the crystal grows and passes through the edge portion of the film 101 made of silicon oxide or the like. It happens.

As a result, ■The tension caused by the difference in impurity concentration is relaxed.

■Crystallinity deteriorates, so leakage current increases.

■Poor crystallinity, so the breaking stress is low.

The present invention solves this problem.

An object of the present invention is to provide a method for manufacturing a vibrating transducer that has good mechanical and electrical properties such as fewer dislocations, a large 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 that is provided on an n-type silicon single crystal substrate, excited by an excitation means, and whose vibrations are detected by an excitation detection means. In the method of manufacturing a vibrating transducer, a shell made of a silicon material is formed so as to surround the vibrating beam and form a chamber with the substrate, and maintain a gap around the vibrating beam. A film of silicon oxide or nitride is formed on a silicon single crystal substrate, a desired portion of the film is removed by etching, and a high concentration film that is difficult to be etched is applied to the portion of the substrate where the vibration beam is to be formed. A first diffusion layer made of P-type silicon is formed by thermal diffusion, the film around the required portion of the film is removed by etching, and an a second diffusion layer of highly concentrated P-type silicon that is easily etched on a portion of the substrate at a position where the substrate-side portion of the chamber is formed by thermal diffusion of the first diffusion layer; A third diffusion layer of highly concentrated P-type silicon, which is easily etched, is formed in a portion of the first epitaxial layer at a position where the shell side portion of the chamber is formed, and the film is removed by etching to form an etching injection hole. , characterized in that an etching fluid is injected through the injection port to remove the twentieth third diffusion layer by selective etching, and the shell is formed by selective epitaxial growth so as to cover the epitaxial layer and close the injection port. This method employs a method of manufacturing a vibrating transducer.

In the above method, after forming the vibrating beam, the gap corresponding part, and the shell corresponding part on the board so as to be integrated with the board,
By removing the portion corresponding to the gap by etching, it is possible to obtain a vibrating transducer in which the substrate, vibrating beam, and shell are integrated.

In addition, a 3X
Since the first diffusion layer made of P-type silicon with a thickness of about 10'''/cm2 or more was formed by thermal diffusion, the first diffusion layer
There is no fear of dislocations occurring in the diffusion layer.

Hereinafter, a detailed explanation will be given based on examples.

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

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

Hereinafter, only the differences from FIGS. 4 to 7 will be explained.

In the figure: (1) As shown in Figure 1 (A), n-type silicon (80
) A silicon oxide or silicon nitride film 201 is formed on the substrate 1 . Required location 202 of membrane 201
is removed by photolithography.

(2) As shown in FIG. 1(B), the vibration beam 3 is attached to the substrate 1,
A second diffusion layer 203 made of P-type silicon and having a thickness of about 3×8″/cm 3 or more is formed at the position where the wafer 4 is formed by thermal diffusion.

(3) As shown in FIG. 1(C), the film 201 around the location 202 is removed and expanded.

(4) As shown in Figure 1 (D), hydrogen (H
2) Hydrogen chloride (HCl) gas is mixed into the source gas in an atmosphere, and the epitaxial layer 204 corresponding to the upper half of the gap 25 and the shell 5 is selectively grown epitaxially using n-type silicon with a phosphorus concentration of 8I7cm-2. .

(5) As shown in FIG. 1(E), the second diffusion layer 205 is formed on the substrate 1 by heat treatment and thermal diffusion of the first diffusion layer 203.
, a third diffusion N206 is formed in the epitaxial layer 204.

(6) As shown in FIG. 1(F), a film 201 of silicon oxide or silicon nitride is coated with hydrofluoric acid (H
F) to remove the etching solution and fill it with the etching solution inlet 2.
07 will be provided.

(7) As shown in Fig. 1<a>, the first diffusion l attachment 203
A positive pulse is applied to the substrate l and the epitaxial layer 204, and an alkaline solution is injected from the etching solution injection port 207 to form the second diffusion layer 205 and the third diffusion layer 20.
6 is selectively etched and removed.

The reason why there is a difference in etching effect between the first diffusion layer 203 and the second diffusion layer 205 or the third diffusion waste 206 is due to the phenomenon that the etching effect is suppressed when the boron concentration exceeds 3X8"am'. .

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

Note that this step is not necessary if the dimensional accuracy is less strict.

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

Note that if the thermal oxidation treatment (8) is not performed, this step is also not necessary.

(9) As shown in Figure 1 (1), hydrogen (H
2) Epitaxial growth of n-type silicon is performed in the etching chamber, an epitaxial growth layer 209 is formed on the outer surface of the substrate 1 and the epitaxial layer 204, and an etching solution injection port 20 is formed.
Close 7.

In addition, since the vibration beam 3.4 and the shell 5 cannot be insulated, the vibration detection signal e is as shown in FIG.
, internal impedance eo of the shell 5: electromotive force Zv of the vibrating beams 3 and 4; becomes the internal impedance of the vibrating beams 3.4 and decreases, but the Q (sharpness of resonance) of the vibrating beams 3 and 4 is sufficiently large. No problem in practical use.

In the above method, the vibration beams 3, 4 and the gap 25 are attached to the substrate 1.
After forming the corresponding portion and the portion corresponding to the shell 5 integrally with the substrate 1, the portion corresponding to the gap 25 is removed by etching, thereby creating a vibrating transducer in which the substrate 1, the vibrating beam 3.4, and the shell 5 are integrated. can be obtained.

In addition, a first silicon plate made of P-type silicon with a size of about 3×8”/cm or more is placed at the position where the vibration beams 3 and 4 are formed on the substrate 1.
Since the diffusion layer 203 is formed by thermal diffusion, fewer dislocations occur in the first diffusion layer 203.

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

(2) Since the crystallinity is improved, the leakage 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 diagram of the main part configuration of an example of the use of a vibrating beam manufactured by the apparatus of the present invention.

In 1, 3 is a vibrating beam. The vibrating beam 3 has two first vibrators 31 that are fixed to the diaphragm 2 at both ends and are arranged parallel to each other, and a second vibrator 32 that mechanically couples the antinode portions of the vibrations of the first vibrators 31 to each other. Equipped with.

Reference numeral 40 applies a DC magnetic field orthogonal to the vibrating beam 3 using the magnet 13, causes an AC current to flow through the both ends of one first vibrator 31 through an input transformer 41, and causes the vibrating beam 3 to move in a direction perpendicular to the magnetic field and current by magnetic induction. It is an excitation means for exciting.

The input cadence 41 has its secondary side connected to both ends of one first vibrator 31 .

Reference numeral 50 denotes vibration detection means for detecting the electromotive force generated at both ends of the other first vibrator 31.

In this case, an output transformer 51 and an amplifier 52 are used.

The primary side of the output transformer 51 is connected to both ends of the other first vibrator 31, and the secondary side is connected to the output terminal 53 via the amplifier 52, and is branched to the input transformer 41.
The positive feedback automatic oscillation circuit is connected to the primary side of the oscillator as a whole.

The vibration of the vibrating beam 3 is detected by the vibration detection means 50 and taken out as an output signal.

In addition, in the above-mentioned embodiment, an example in which the present invention is applied to a pressure sensor has been described, but the present invention is not limited to this, and it goes without saying that the present invention may be applied to, for example, a temperature sensor or an acceleration sensor.

Furthermore, the above-mentioned manufacturing method can be applied not only to the vibrating beam 3.4 which is fixed at both ends, but also to a cantilever beam or a plurality of fixed beams.

<Effects of the Invention> As explained above, the present invention provides a vibrating beam made of a silicon single crystal material provided on an n-type silicon single crystal substrate, excited by an excitation means, and detected by an excitation detection means. and forming a shell made of a silicon material surrounding the vibrating beam to form a chamber with the substrate and maintaining a gap around the vibrating beam, the method comprising: A film of silicon oxide or nitride is formed on the silicon oxide or nitride film, and required portions of the film are removed by etching, and a film made of high-concentration P-type silicon that is difficult to be etched is deposited on the part of the substrate where the vibrating beam is to be formed. 1. A diffusion layer is formed by thermal diffusion, and the film around the required portion of the film is removed by etching, and 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 to be formed. A second diffusion layer of high concentration P-type silicon, which is easily etched in a portion of the substrate at a position where the substrate side portion of the chamber is formed by thermal diffusion of the first diffusion layer, is formed in the first epitaxial layer. A third diffusion layer of highly concentrated P-type silicon that is easily etched is formed in a portion where the shell side portion of the chamber is to be formed, and the film is removed by etching to form an etching injection port, and etching is performed from the injection port. Manufacturing a vibrating transducer characterized in that a fluid is injected, the 20th third diffusion layer is removed by selective etching, and the shell is formed by selective epitaxial growth so as to cover the epitaxial layer and close the injection port. method was adopted.

As a result, ① The residual strain (tension) in the vibrating beam due to the difference in impurity concentration can be kept large.

- Improved crystallinity reduces leakage current in the vibrating beam.

■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 for manufacturing a vibrating transducer that has good mechanical and electrical characteristics such as fewer dislocations, a large initial tension, and high sensitivity.

[Brief explanation of drawings]

Fig. 1 is a process explanatory diagram of an embodiment of the present invention, Fig. 2 is an explanatory diagram of operation, Fig. 3 is an explanatory diagram of use, and Figs. 4 to 7 are configurations of conventional examples commonly used. The explanatory diagram, FIG. 8, is an explanatory diagram of the manufacturing process of Japanese Patent Application No. 159073/1982 entitled "Title of the invention: Method for manufacturing a vibrating transducer". DESCRIPTION OF SYMBOLS 1... Substrate, 13... Magnet, 2... Pressure receiving diaphragm, 3.4... Vibration beam, 20... Notch part, 21
a, 21b, 23...21 layer, 22...n type epitaxial layer, 24...5102.25... gap part,
31... first vibrator, 32... second vibrator, 40...
. . . Excitation means, 41 .
...Membrane, 202...Location, 203...First diffusion layer, 204...Epitaxial layer, 205...Second diffusion layer, 206...Third diffusion layer, 207...Etching Liquid injection port, 208... silicon oxide film, 209.
...Epitaxial layer. Figure 1 Figure 0SC Figure 1 Cow Figure Etaite 18 Extraction Figure 2 Flam

Claims (1)

[Claims] A vibrating beam made of a silicon single crystal material 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, and the substrate is surrounded by the vibrating beam. A method for manufacturing a vibrating transducer in which a shell made of a silicon material is formed to form a chamber and a gap is maintained around the vibrating beam, the method comprising: forming a silicon oxide or nitride film on the silicon single crystal substrate; A first diffusion layer made of highly-concentrated P-type silicon that is difficult to be etched is formed on the substrate at a position where the vibration beam is to be formed by thermal diffusion. , removing the film around the required part of the film by etching, forming an epitaxial layer made of n-type silicon on the shell side part of the chamber and the part where the shell is to be formed, and A second diffusion layer of high-concentration P-type silicon, which is easily etched by thermal diffusion at a portion of the substrate at a position where the substrate side portion of the chamber is formed, is formed on the shell side portion of the chamber of the first epitaxial layer. forming a third diffusion layer of highly concentrated P-type silicon that is likely to be etched, removing the film by etching to form an etching injection port, and injecting an etching fluid through the injection port to A method for manufacturing a vibrating transducer, characterized in that the diffusion layer is removed by selective etching, and the shell is formed by selective epitaxial growth so as to cover the epitaxial layer and close the injection port.