JPH0254136A - Preparation of oscillation type transducer - Google Patents

Abstract

PURPOSE:To reduce transposition, to increase initial tension and to enhance sensitivity, by forming an oscillation beam, a gap corresponding part and a shell phase part to a substrate integrally and subsequently removing the gap corresponding part by etching. CONSTITUTION:A film 20 composed of silicon oxide or silicon nitride is formed to a substrate 1 and the required place 202 of the film 201 is removed by photolithography. Subsequently, the first diffusion layer 203 composed of P-type silicon of below 3X10<1g>/cm<2> is formed to the substrate 1 at the part of a gap part on the substrate side and the part of a position where an oscillation beam is formed by thermal diffusion. Next, the second diffusion layer 204 composed of P-type silicon of about 3X10<1g>/cm<2> or more is formed at the part of the position where the oscillation beam of the first diffusion layer 203 is formed by thermal diffusion. As a result, the transposition generated in the second diffusion layer 204 is reduced. Further, the tension of the oscillation beam due to impurity concn. difference is largely held.

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. 5 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, and Fig. 6 is a diagram showing the configuration of a conventional example commonly used.
The XX sectional view in the figure and FIG. 7 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. 5 for clarity.

FIG. 8 is an enlarged sectional view showing the vicinity of the vibrating beam in FIG. 6. 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 P ten layer, and 218.21b is the notch 20
electrically isolated by

22 is an n-type epitaxial layer, 23 is a P ten layer, 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 constituted by a P layer and a SiO2 layer that are fixed at both ends and span the gap 25.

In FIG. 8, two layers 23 forming the vibrating beam 3 (4),
One layer 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-layer 23; 21b and the P layer 23, the vibration beam 3 (4)
It is designed to detect vibrations.

oSC is an oscillation circuit, and this circuit is configured externally or using a 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 terminal is connected to the P10 layer 21a, and provides an output signal between the P+W 121a and the P+ layer 23.

As a result, the oscillation circuit O8C and the vibration beam 3 (4) constitute a self-excited oscillation circuit that oscillates at the natural frequency of the vibration #J 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 vibrations #3 and 3, and a compressive force is applied to the vibration beam 4 formed at the peripheral edge of the diaphragm 2. As a result, the natural frequencies f, f2 of each vibrating beam 3, 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. can do.

Since the shell 5 places the vibrating beams 3, 4 in a vacuum, 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.
Title of invention: "Method for manufacturing a vibrating transducer" has been filed.

This application will be explained below with reference to FIG.

In the figures, the same symbols as in FIGS. 5 to 8 indicate the same functions.

Hereinafter, only the differences from FIGS. 5 to 8 will be explained.

(1) As shown in Figure 9(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. Required portions of the film 101 are removed by photolithography.

(2) As shown in Figure 9 (B), hydrogen (
H2) Etching is performed with hydrogen chloride in an atmosphere to etch required portions 102 on the substrate 1 to undercut WAlo1 and form recesses 103.

Note that instead of hydrogen chloride, 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 9 (C), hydrogen (
H2) atmosphere, the source gas contains hydrogen chloride (1(CI)
) A selective epitaxial growth method is performed by mixing gas.

In other words, ■Boron? A first epitaxial layer M104 corresponding to the lower half of the gap 25 is selectively grown epitaxially using P-type silicon of JC10' cm-.

■ P-type silicon with a boron concentration of 10"am"3,
At a required location 10 on the surface of the first epitaxial layer 104
A second epitaxial layer 105 corresponding to the vibrating beam 3.4 is selectively grown epitaxially so as to cover the vibrating beam 3.4.

■ P-type silicon with a boron concentration of 10"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 second epitaxial layer 105 .

■N-type silicon with a phosphorus concentration of 10"cm'
A fourth epitaxial layer 107 corresponding to the shell 5 is selectively epitaxially grown on the surface of the epitaxial layer 106 .

(4) As shown in FIG. 9 (D>), a film 101 of silicon oxide or silicon nitride is coated with hydrofluoric acid (H
Remove it by etching with step F) and insert the etching solution inlet 1.
08 will be provided.

(5) As shown in FIG. 9 (E>), with respect to the second epitaxial layer 105, 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
04 or the third epitaxial layer 106 because the boron concentration is 3X10'
This is because when the thickness exceeds 3 cm, the etching action is suppressed.

This is shown, for example, in Fig. 8 of "Transducers 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.
Namazashinuru.

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

(7) As shown in FIG. 9(p), the substrate 1 and the 4-1: bitaxial layer 10 are etched by plasma etching.
The silicon oxide film 109 on the outer surface of 7 is removed. In addition,
If the thermal oxidation treatment (7) is not performed, this step is not necessary.

(8) As shown in Figure 9 (G), hydrogen (H
2) Perform epitaxial growth of n-type silicon in the
An epitaxial growth layer 111 is formed on the outer surfaces of the substrate 1 and the fourth epitaxial layer 107, and the etching solution injection port 108 is closed.

In addition, 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 vibration beam 3.4, and the shell 5 are integrally formed, there is no need to bond the substrate 1 and the shell 5, and the problem of instability due to bonding is avoided. It disappears.

(2) With a simple structure, the vibrating beams 3 and 4 can be insulated from 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. Likely to happen.

As a result, ■The silver strength due to the difference in impurity concentration is alleviated.

■Crystallinity deteriorates, so the 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 (large initial tension and high sensitivity).

Means for Solving the Problems To achieve this object, the present invention provides a silicon single crystal material that is provided on a silicon single crystal substrate, excited by an excitation means, and whose vibrations are detected by an excitation detection means. In a method for manufacturing a vibrating transducer, the method includes forming a vibrating f#J beam, surrounding the vibrating beam to form a chamber with the substrate, and forming a shell made of silicon material so as to maintain a gap around the vibrating beam, A film of silicon oxide or nitride is formed on the silicon single crystal substrate, and required portions of the film are removed by etching, and the substrate (l) portion of the chamber and the vibrating beam are formed on the substrate. After forming a first diffusion layer made of high-concentration P-type silicon, which is easily etched, by thermal diffusion,
A method for manufacturing a vibrating transducer characterized in that a second diffusion layer made of highly concentrated P-type silicon that is difficult to be etched is formed by thermal diffusion in a portion of the diffusion layer where the vibrating beam is formed. It is.

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.

Further, since the second diffusion layer made of highly-concentrated P-type silicon, which is difficult to be etched, is formed by thermal diffusion in the portion of the substrate where the vibrating beam is to be formed, there is no fear of dislocations occurring in the second 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. 5 to 8 represent the same functions.

Hereinafter, only the differences from FIGS. 5 to 8 will be explained.

(1) As shown in Figure 1 (A), n-type silicon (10
0) A silicon oxide or silicon nitride film 201 is formed on the substrate 1. Required part 20 of a201
2 is removed by photolithography.

(2) As shown in FIG. 1(B), there is a gap 25 in the substrate 1.
A first diffusion layer 203 made of P-type silicon with a thickness of less than about 3×10"/am' is formed by thermal diffusion on the substrate side portion and the portion where the vibrating beams 3 and 4 are to be formed.

(3) As shown in FIG. 1(C), the portion of the first diffusion layer 203 where the vibration beam 3.4 is formed is 3
A second diffusion layer 204 made of P-type silicon of approximately mco or more
(4) As shown in Figure 1 (D), HCl gas is mixed into the source gas in a hydrogen (H2) atmosphere at 1050°C to obtain a boron concentration of 1018 cm''3.
The first epitaxial layer 206 corresponding to the upper half of the gap 25 is selectively epitaxially grown using P-type silicon of less than 100 mL.

(5) As shown in Figure 1 (E), hydrogen (
H2) HC1' gas is mixed into the source gas in an atmosphere, and the surface of the first epitaxial layer 205 is coated with P-type silicon having a boron concentration of 3 x 10' cm3 or more.
A second epitaxial layer 206 corresponding to shell 5 is selectively epitaxially grown.

(6) As shown in Figure 1<F), silicon oxide or silicon nitride II! 201 is removed by etching with hydrofluoric acid (HF), and one inlet 207 for an etching solution is provided.

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

The reason why there is a difference in etching effect between the second diffusion layer 204 and the first diffusion layer 203 or the first epitaxial layer 205 is that when the boron concentration exceeds 3X10'' cm, a phenomenon that suppresses the etching effect occurs. by.

(8) As shown in FIG. 1(H), thermal oxidation treatment is performed to produce silicon oxide pA208 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 second epitaxial layer 206 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 (I), hydrogen (
Perform epitaxial growth of n-type silicon in H2),
On the outer surfaces of the substrate 1 and the second epitaxial ffJ206,
An epitaxial growth layer 209 is formed, and the etching solution injection port 207 is closed.

In addition, this process is (2) Close the etching solution injection port 207 by thermal oxidation.

(2) A film of polysilicon is deposited on the etching solution injection port 207 by CVD or sputtering, and the etching solution injection port 207 is closed.

(2) Filling the etching solution injection port 207 by silicon epitaxial method using vacuum evaporation method.

(2) The etching solution injection port 207 may be filled with an insulator such as glass (SiOz), nitride, alumina, etc. by CVD, sputtering, or vapor deposition.

Note that since the vibration beam 3.4 and the shell 5 cannot be insulated, the a motion detection signal e is expressed as e= (Zs −eQ ) / (Zv
-G Zs) Zs; internal impedance eo of shell 5 + electromotive force Zv of vibrating beams 3 and 4; internal impedance of vibrating beams 3 and 4 decreases, but Q of vibrating beam 3.4 <resonance sharpness ) is sufficiently large that it does not pose a practical problem.

Further, the first epitaxial layer 205 may be n-type silicon.

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 beams 3, 4, and the shell 5 are integrated. can be obtained.

In addition, since the second diffusion layer 204 made of P-type silicon of approximately 3×10"/am' or more was formed by thermal diffusion at the position where the vibration beams 3 and 4 are formed on the substrate 1, the second diffusion layer 204 Fewer dislocations occur.

As a result, ■Residual strain (tension) in vibrating beam 3.4 due to impurity concentration difference
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 view of the main part manufacturing process of another embodiment of the present invention.

In the figure, (1) As shown in Figure 3 (A>), n-type silicon (10
0) A silicon oxide or silicon nitride film 201 is formed on the substrate 1. [Required part 20 of 201
2 is removed by photolithography.

(2) As shown in FIG. 3(B), there is a gap 25 in the substrate 1.
A first diffusion layer 203 made of P-type silicon and having a thickness of less than about 3×10″/cm′ is formed by thermal diffusion on the substrate side portion and the portion where the vibrating beams 3 and 4 are to be formed.

(3) As shown in Fig. 3 <C), 3x IQ is applied to the portion of the first diffusion layer 203 where the vibration beam 3.4 is formed.
A second diffusion layer 204 made of P-type silicon with a l 9 / Cm 2 or more is formed by thermal diffusion. (4) As shown in FIG. Hydrogen chloride (MCI and silane (Si)
H4) By mixing gas, the concentration of phosphorus is 10"cm"3.
A fifth epitaxial layer M211 corresponding to the upper half of the gap 25 and the shell 5 is selectively grown epitaxially using molded silicon.

In this case, since etching by hydrogen chloride and crystal growth proceed simultaneously on the surface of the second diffusion layer 204, boron comes out (Out Diffusion).
iffusion).

(5) As shown in FIG. 3(F), the P-type layer 2111 grows to a point where the concentration of boron is higher than the concentration of phosphorus (1017 cm') in the growing silicon.

(6) As shown in FIG. 3(F), when the boron concentration decreases, an n-type layer 2112 grows.

(7) As shown in FIG. 3(G), a film 201 of silicon oxide or silicon nitride is coated with hydrofluoric acid (H
P) to remove it by etching, and then insert the etching solution inlet 2.
07 will be provided.

(7) As shown in FIG. 3(H), a positive pulse is applied to the second diffusion layer 204, the substrate 1 and the second epitaxial layer 206, and an alkaline solution is injected from the etching solution injection port 207. Then, the first diffusion layer 203 and the P-type layer 211
1 is selectively etched and removed.

The reason why there is a difference in etching effect between the second diffusion layer 204 and the first diffusion layer 203 or the P-type layer 2111 is due to the phenomenon that the etching effect is suppressed when the boron concentration exceeds 3×101 gcm'.

(8) As shown in FIG. 3(I), 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 higher.

By plasma etching process, the substrate 1 and the n-type layer 21 are
The silicon oxide film 208 on the outer surface of 12 is removed.

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

(9) As shown in Figure 3 (J), hydrogen (
1 (2), epitaxial growth of nl silicon is performed, epitaxial growth W1212 is formed on the outer surfaces of the substrate 1 and the n-type layer 2112, and an etching solution injection port 20 is formed.
Close 7.

FIG. 4 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 the figure, 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 perpendicular to the vibrating beam 3 using a magnet 13, and an alternating current is applied to both ends of one first vibrator 31 by an inductor transformer 41, so that the vibrating beam 3 is moved in a direction perpendicular to the magnetic field and the current by magnetic induction. This is an excitation means that excites the

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 forms a vibrating beam made of a silicon single crystal material, which is provided on a silicon single crystal substrate, excited by an excitation means, and whose vibrations are detected by an excitation detection means. A chamber is formed with the substrate surrounding the vibrating beam, and the 1i
It! A method for manufacturing a vibrating transducer in which a shell made of a silicon material is formed so as to maintain a gap around an IJ beam, comprising: forming a silicon oxide or nitride film on the silicon single crystal substrate; A first diffusion layer made of high-concentration P-type silicon, which is easily etched, is formed on the substrate by thermal diffusion on the substrate side portion of the chamber and the portion where the vibration beam is to be formed. After that, a second diffusion layer made of highly-concentrated P-type silicon that is difficult to be etched is formed by thermal diffusion on a portion of the first diffusion layer where the vibration beam is formed. 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 properties such as fewer dislocations, a large initial tension, and high sensitivity.

[Brief explanation of the drawing]

Fig. 1 is a process explanatory diagram of one embodiment of the present invention, Fig. 2 is an operation explanatory diagram, Fig. 3 is a process explanatory diagram of another embodiment of the present invention, Fig. 4 is a usage explanatory diagram, and Fig. 5 is an explanatory diagram of the process of an embodiment of the present invention. Figure 8 is an explanatory diagram of the configuration of a conventional example that has been generally used, and Figure 9 is a patent application filed in 1983.
2-159073 ``Title of the invention: Method for manufacturing a vibrating transducer'' is an explanatory diagram of the manufacturing process. DESCRIPTION OF SYMBOLS 1... Substrate, 13... Magnet, 2... Pressure receiving diaphragm, 3.4... Vibration beam, 20... Notch part, 21
a, 21b 23...P ten layers, 22...n-type epitaxial layer, 24...5i02.25...gap, 31...first vibrator, 32...second vibrator , 40
...Excitation means, 41...Input cadence, 42...
Input terminal, 50... Vibration detection means, 51... Output transformer, 52... Amplifier, 53... Output terminal, 20
DESCRIPTION OF SYMBOLS 1... Membrane, 202... Location, 203... First diffusion layer, 204... Second diffusion layer, 205... First epitaxial layer, 206... Second epitaxial layer, 20
7... Injection of etching solution [], 208... Silicon oxide film, 209... Epitaxial layer, 211...
・Fifth Ebitakal layer, 2111... P-type layer, 21
12...n-type layer, 212...Evitacal layer. Figure 1 Figure 2 S (B) Figure 3 (D) (F) Figure 9

Claims (1)

[Claims] A vibration beam made of a silicon single crystal material is provided on a silicon single crystal substrate, excited by an excitation means, and vibration is detected by an excitation detection means, and is surrounded by the vibration beam and connected to the substrate and a chamber. and forming a shell made of silicon material so as to maintain a gap around the vibrating beam, the method comprising: forming a silicon oxide or nitride film on the silicon single crystal substrate; Then, required portions of the film are removed by etching, and a first diffusion layer made of high-concentration P-type silicon that is easily etched is formed on the substrate in the substrate-side portion of the chamber and in the portion where the vibration beam is to be formed. A vibration device characterized in that after forming by thermal diffusion, a second diffusion layer made of highly concentrated P-type silicon that is difficult to be etched is formed by thermal diffusion in a portion of the first diffusion layer at a position where the vibration beam is formed. Manufacturing method for shaped transducers.