JPH07101750B2 - Vibratory Transducer Manufacturing Method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a vibrating transducer having a vibrating beam, which is provided on a silicon single crystal substrate and is made of a silicon single crystal material. .

More specifically, the present invention relates to a method for manufacturing a vibrating transducer having a large initial tension and a large operating range.

<Prior Art> FIG. 4 is a structural explanatory view of a conventional example which 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, 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 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. 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 and 21b are P ⁺ layers, which are 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 that straddles 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 the working is excited by utilizing an electrostatic force between the P ⁺ layer 23, also an 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.

The output terminal is connected to the P ⁺ layer 21a, it provides an output signal between the P ⁺ layer 21a and the P ⁺ layer 23. As a result, the oscillator circuit 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 3,
Natural frequency f _1, f ₂ of 4 differentially become change that the pressure P, for example, by calculating the difference between f ₁ -f _2, it is possible to measure the pressure P.

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 an apparatus, 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.

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. 63-86946, entitled "Invention; Manufacturing method of vibrating transducer", filed on April 8, 1988.

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

In the figure, the same symbols as those 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) As shown in FIG. 8 (B), etching is performed with hydrogen chloride in a hydrogen (H ₂ ) atmosphere at 1050 ° C. to etch a required portion 102 on the substrate 1 to undercut the film 101, The recess 103 is formed.

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. 8 (C), 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 .

Boron concentration of 3 × 10 ¹⁸ cm ^-3 P type silicon
The second epitaxial layer 1 corresponding to the vibrating beams 3 and 4 is formed on the surface of the first epitaxial layer 104 so as to close the required portion 102.
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 106 corresponding to the upper half of the gap 25 is selectively epitaxially grown on the surface of the epitaxial layer 105.

Boron concentration of 3 × 10 ¹⁸ cm ^-3 P type silicon
A fourth epitaxial layer 107 corresponding to shell 5 is selectively epitaxially grown on the surface of the third epitaxial layer 106.

(4) As shown in FIG. 8 (D), silicon oxide,
Alternatively, the silicon nitride film 101 is treated with hydrofluoric acid (H
It is etched away in F) and an etching injection port 108 is provided.

(5) As shown in FIG. 8 (E), a positive pulse is applied to the substrate 1 with respect to the fourth layer, and the etchant injection port 10 is formed.
Injecting an alkaline solution from 8 to form the first epitaxial layer 104
Then, the third 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) As shown in FIG. 8 (F), n-type silicon is epitaxially grown in hydrogen (H ₂ ) at 1050 ° C. to form the second epitaxial layer 105 and the fourth epitaxial layer 1.
A fifth epitaxial layer 109 made of n-type silicon is formed so as to cover 07 and the surface of the substrate 1 on the side of the recess 103 and close the injection port 108, and the etching injection port 108 is closed.

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 silicon oscillators 3 and 4 formed by alkali selective etching using a boron high-concentration layer have an atomic radius of boron smaller than that of silicon. , There is internal stress (tension).

Since the oscillators 3 and 4 have a problem that the operation region on the compression side is limited by buckling, this internal stress is positively utilized.

On the other hand, in the step of sealing the injection port 108 shown in FIG. 8F, the n-type fifth epitaxial layer 111 also grows on the surface of the second epitaxial layer 105 corresponding to the oscillators 3 and 4.

Since no internal stress is generated in the fifth epitaxial layer 111, the initial tension of the oscillators 3 and 4 is reduced, and the operating range of the oscillators 3 and 4 on the compression side is narrowed.

The present invention solves this problem.

An object of the present invention is to provide a method for manufacturing a vibrating transducer having a large initial tension and a large operating range.

<Means for Solving the Problems> In order to achieve this object, the present invention is provided on a substrate of a silicon single crystal, vibration is detected by the excitation detection means excited by the excitation means from the silicon single crystal material 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 the surface of the cavity layer where the vibrating beam is to be formed, and the second side of the chamber where the shell side 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. Removing by etching to form an etching injection port, injecting an etching fluid from the injection port to remove the first and second epitaxial layers by selective etching, and removing the second epitaxial layer, the fourth epitaxial layer and the substrate. Cover the surface on the concave side and close the injection port Is obtained by employing the method for manufacturing the vibration type Toransudeyusa, characterized in that the epitaxially grown by doping Unishi simultaneously carbon and phosphorus fifth epitaxial layer made of n-type silicon Te in silicon.

<Operation> In the method described above, in the step of sealing the injection port, the fifth epitaxial layer grown on the surface of the second epitaxial layer corresponding to the vibrator is epitaxially grown by doping carbon into silicon at the same time as phosphorus. 5
Since the internal stress exists in the epitaxial layer, the initial tension of the oscillator does not decrease.

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. 4 to 7 represent the same functions.

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

(1) As shown in FIG. 1 (A), n-type silicon (10
A film 201 of silicon oxide or silicon nitride is formed on the substrate 1 cut in the 0) plane. The required parts of the film 201 are removed by photolithography.

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

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. 1 (C), 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 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. 1 (D), silicon oxide,
Alternatively, the silicon nitride film 201 may be replaced with hydrofluoric acid (H
It is etched away in step F) and an etching injection port 208 is provided.

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

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) As shown in FIG. 1 (F), the n-type silicon is epitaxially grown in hydrogen (H ₂ ) at 1050 ° C. to form the second epitaxial layer 205 and the fourth epitaxial layer 2.
The fifth epitaxial layer 211 made of n-type silicon is epitaxially grown by doping carbon into silicon at the same time as phosphorus so as to cover the surface of 07 and the substrate 1 on the side of the concave portion 203 and close the injection port 208, and to etch. Close the inlet 208.

In this case, methane gas (CH ₄ ) etc. is used.

Since the vibration beams 3 and 4 and the shell 5 cannot be insulated, the vibration detection signal e is e = (Z _s · e _o ) / (Z _v + Z _s ) Z _s as shown in FIG. The internal impedance of shell 5 e _o ; the electromotive force of the vibrating beams 3 and 4 Z _v ; the internal impedance of the vibrating beams 3 and 4, which decreases, but the Q (resonance sharpness) of the vibrating beams 3 and 4 decreases. Since it is large enough, there is no practical problem.

In the above method, in the step of sealing the injection port 208,
The fifth epitaxial layer 209, which grows on the surface of the second epitaxial layer 205 corresponding to the oscillators 3 and 4, is epitaxially grown by doping carbon into silicon at the same time as phosphorus, and internal stress exists in the fifth epitaxial layer 209. Since this is done, the initial tension of the oscillators 3 and 4 does not decrease.

As a result, it is possible to obtain a method of manufacturing a vibratory transducer in which the operating ranges of the vibrators 3 and 4 are wide.

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 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, 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.

<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 silicon single crystal substrate and whose vibration is detected by the excitation detection means excited by the excitation means. A method of manufacturing a vibrating transducer, which encloses the vibrating beam to form 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 film of silicon 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 portion of the chamber is formed. Selectively epitaxially growing a first epitaxial layer of a high concentration of P-type silicon that is easily etched on a portion of 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 in a portion where the moving beam is formed, and a high-concentration P-type that is easily etched in a portion where the shell side portion of the chamber is formed A third epitaxial layer of silicon is selectively epitaxially grown, and a fourth epitaxial layer of high-concentration P-type silicon that is difficult to be etched is selectively epitaxially grown to cover the third epitaxial layer, and the film is removed by etching to form an etching injection hole. And then etching liquid is injected from the injection port to remove the first and second epitaxial layers by selective etching to cover the second epitaxial layer, the fourth epitaxial layer, and the concave surface of the substrate. Together with the n-type silicon so as to block the inlet. A fifth epitaxial layer made of adopting the method for manufacturing the vibration type Toransudeyusa, characterized in that the epitaxially grown by doping phosphorus at the same time as the carbon in the silicon.

In the above method, in the step of sealing the injection port, the fifth epitaxial layer grown on the surface of the second epitaxial layer corresponding to the vibrator is epitaxially grown by doping carbon into silicon simultaneously with phosphorus,
Since the internal stress exists in the fifth epitaxial layer, the initial tension of the vibrator does not decrease.

As a result, it is possible to obtain a method of manufacturing a vibrating transducer in which the operating range of the vibrator is wide.

Therefore, according to the present invention, it is possible to realize a method of manufacturing a vibrating transducer having a large initial tension and a large operating range.

[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. Explanatory drawing and FIG. 8 are manufacturing process explanatory drawings of Japanese Patent Application No. 63-86946 "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, 210 …… membrane, 202 …… location, 203 …… recess, 2
04 …… first epitaxial layer, 205 …… second epitaxial layer, 206 …… third epitaxial layer, 207 …… fourth epitaxial layer, 208 …… etching injection port, 209 …… fifth 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 Incorporated (56) References JP-A-62-63828 (JP, A) JP-A-2-36576 (JP, A)

Claims (1)

[Claims] 1. A vibrating beam, which is provided on a silicon single crystal substrate, is excited by an exciting means, and vibration is detected by an excitation detecting means to form a vibrating beam made of a silicon single crystal material. The vibrating beam is surrounded and the substrate and the chamber are surrounded. In the method of manufacturing a vibrating transducer in which a shell made of a silicon material is formed so that a gap is maintained around the vibrating beam, a silicon oxide or nitride film is formed on the silicon single crystal substrate. , 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-type that is easily etched in a portion of the chamber where a substrate side is formed Selectively epitaxially grow a first epitaxial layer made of silicon, and etch the surface of the first epitaxial layer at a position where the vibrating beam is formed. Selective epitaxial growth of a second epitaxial layer of high concentration P-type silicon that is difficult to etch, and selective epitaxial growth of a third epitaxial layer of high concentration P-type silicon that is easily etched in the portion where the shell side portion of the chamber is formed. Then, 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 is selectively epitaxially grown, and the film is removed by etching to form an etching injection port. And removing the first and second epitaxial layers by selective etching to cover the second epitaxial layer, the fourth epitaxial layer, and the surface of the substrate on the side of the recess, and to block the injection port. The fifth epitaxial layer made of silicon Method for manufacturing a vibration type Toransudeyusa, characterized in that the epitaxially grown by doping carbon in silicon at the same time.