JPH0590616A - Manufacture of vibrating-type transducer - Google Patents

Abstract

PURPOSE:To contrive to miniaturize an apparatus at a low cost by subjecting a first layer in a part corresponding to the lower half of a vacuum chamber and a second layer corresponding to a vibrating beam to a selective epitaxial growth, further by causing third and fourth layers to grow and by making the first and third layers porous and oxidizing them through anodizing. CONSTITUTION:A first epitaxial layer corresponding to the lower half of a vacuum chamber and second epitaxial layer 205 corresponding to a vibrating beam 3 are subjected to a selective epitaxial growth by P-type silicon and N-type silicon, respectively. A third epitaxial layer 206 corresponding to the upper half of the vacuum chamber and a fourth epitaxial layer 207 corresponding to a shell are subjected to the selective epitaxial growth. A silicon oxide or silicon nitride film 201 is removed by etching through hydrofluoric acid so that an etching filler hole 208 is provided. The first epitaxial growth layer 204 and third epitaxial growth layer 206 are made porous and oxidized by anodizing in hydrofluoric acid. The second and fourth epitaxial growth layers 205 and 207 are not made porous.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a vibratory transducer which can be miniaturized at low cost.

[0002]

2. Description of the Related Art FIG. 10 is an explanatory view of a main part configuration of a conventional example which has been generally used in the past.
No. 176, title of the invention, "Method of Manufacturing Vibration Transducer", is filed on July 2, 1987. 11
FIG. 11 is a sectional view taken along line AA of FIG. 10.

In the figure, 1 is a semiconductor single crystal substrate, and 2
Is a measuring diaphragm which is provided on the semiconductor substrate 1 and receives the measuring pressure Pm. Reference numeral 3 is a strain detection sensor embedded in the measurement diaphragm 2, and a vibrating beam 3 is used. Reference numeral 4 denotes a shell made of a semiconductor epitaxial growth layer for sealing, which seals the vibrating beam 3 in the measurement diaphragm 2.
A vacuum chamber 5 is provided around the vibrating beam 3 and between the vibrating beam 3 and the measuring diaphragm 2 and the shell 4. The vibrating beam 3 is oscillated by the natural vibration of the vibrating beam 3 by the magnetic field of the permanent magnet (not shown) and the closed loop self-excited oscillation circuit (not shown) connected to the vibrating beam 3. It is configured.

In the above configuration, the measurement diaphragm 2
When the measurement pressure Pm is applied to the, the axial force of the vibrating beam 3 changes,
Since the natural frequency changes, the measurement pressure Pm can be measured by changing the oscillation frequency.

12 to 17 are examples of manufacturing illustrations of the conventional example of FIG. 10, for example, Japanese Patent Application Laid-Open No. 1-258475, Japanese Patent Application No. 63-86946, and the title of the invention filed by the applicant of the present application. "Method for manufacturing vibrating transducers", Showa 6
It is shown in the application filed on April 8, 3rd.

12 to 17 will be described below. (1) As shown in FIG. 12, a film 101 of silicon oxide or silicon nitride is formed on the substrate 1 cut into the n-type silicon (100) plane. The required portion 102 of the film 101 is removed by photolithography. (2) As shown in FIG. 13, hydrogen (H ₂ ) at 1050 ° C.
Etching is performed with hydrogen chloride in an atmosphere to etch a required portion 102 of the substrate 1 and undercut the film 101 to form a recess 103. Instead of hydrogen chloride, high temperature steam or oxygen may be used, or anisotropic etching with an alkali solution at 40 ° C to 130 ° C may be used.

(3) As shown in FIG. 14, in a hydrogen (H ₂ ) atmosphere at 1050 ° C., hydrogen chloride gas is mixed with a source gas to perform a selective epitaxial growth method. That is, the first epitaxial layer 104 corresponding to the lower half of the vacuum chamber 5 is made of P-type silicon having a boron concentration of 10 ¹⁸ cm ^−3.
Are selectively epitaxially grown. A second epitaxial layer 105 corresponding to the vibrating beam 3 is selectively epitaxially grown on the surface of the first epitaxial layer 104 using P-type silicon having a boron concentration of 3 × 10 ¹⁹ cm ⁻³ so as to block the required portion 102. A third epitaxial layer 106 corresponding to the upper half of the vacuum chamber 5 is selectively epitaxially grown on the surface of the second epitaxial layer 105 with P-type silicon having a boron concentration of 10 ¹⁸ cm ^-3 . A fourth epitaxial layer 107 corresponding to the shell 4 is selectively epitaxially grown on the surface of the third epitaxial layer 106 with P-type silicon having a boron concentration of 3 × 10 ¹⁹ cm ⁻³ .

(4) As shown in FIG. 15, the silicon oxide or silicon nitride film 101 is removed by etching with hydrofluoric acid (HF) to provide an etching injection port 108. (5) As shown in FIG. 16, a positive pulse or a positive voltage is applied to the substrate 1 with respect to the fourth layer, and an alkali solution is injected from the etching injection port 108 to form the first epitaxial layer 104 and the third The epitaxial layer 106 is removed by selective etching. A hydrazine solution is generally used as the etching solution. Second epitaxial layer 105 and first epitaxial layer 1
04 or the third epitaxial layer 106 has a difference in etching action because the boron concentration is 3 × 10 ^19.
This is because when the ^{density is} more than cm ^{−3, the} phenomenon of suppressing the etching action occurs.

(6) As shown in FIG. 17, n-type silicon is epitaxially grown in hydrogen (H ₂ ) at 1050 ° C. to form an epitaxial growth layer 111 on the outer surfaces of the substrate 1 and the fourth epitaxial layer 107. The etching inlet 108 is closed. In this step, the etching inlet 108 is closed by thermal oxidation. Polysilicon is deposited on the portion of the etching inlet 108 by the CVD method or the sputtering method, and the etching inlet 108 is closed. The etching injection port 108 is filled with the silicon epitaxial method by the vacuum evaporation method. The etching inlet 108 may be filled with an insulating material such as glass (SiO ₂ ), nitride, or alumina by the CVD method, the sputtering method, or the vapor deposition method.

[0010]

However, in such a device, the first epitaxial layer 104 and the third epitaxial layer 104
In order to remove the epitaxial layer 106 by selective etching, an alkaline aqueous solution is generally used as an etching solution. However, since the alkaline aqueous solution requires a wide gap as the etching inlet 108, the epitaxial growth layer 111 grows thick on the vibrating beam 3 during sealing, and the vibrating transducer cannot be miniaturized.

The present invention solves this problem. An object of the present invention is to provide a method of manufacturing a vibratory transducer that can be made compact at low cost.

[0012]

To achieve this object, the present invention provides a vibrating beam provided on a silicon single crystal substrate, and the vibrating beam so that a gap is maintained around the vibrating beam. A method for manufacturing a vibrating transducer comprising: a shell made of a silicon material that surrounds the substrate and a vacuum chamber; an exciting unit that excites the vibrating beam; and an exciting detecting unit that detects vibration of the vibrating beam. A method of manufacturing a vibration type transducer having the following steps is adopted. (A) A step of forming a silicon oxide or silicon nitride film on an n-type substrate. (B) A step of removing a required portion of the film by photolithography. (C) A step of forming a first layer of P-type silicon by selective epitaxial growth or diffusion in a portion corresponding to the lower half of the vacuum chamber. (D) A step of selectively epitaxially growing a second layer corresponding to the vibrating beam on the surface of the first layer with n-type silicon so as to close the required portion. (E) A step of selectively epitaxially growing a third layer corresponding to the upper half of the vacuum chamber on the surface of the second layer with a high concentration of P-type silicon that is easily etched. (F) A step of selectively epitaxially growing a fourth layer corresponding to the shell on the surface of the third layer with n-type silicon. (G) A step of etching and removing the silicon oxide or silicon nitride film to provide an etching injection port. (H) In hydrofluoric acid, light is irradiated to perform anodization treatment,
The step of making the first layer and the third layer porous. (I) A step of oxidizing the porous first layer and third layer. (J) A step of removing the first layer and the third layer with hydrofluoric acid.

[0013]

In the above manufacturing method, a silicon oxide or silicon nitride film is formed on the n-type substrate. The required parts of the film are removed by photolithography. In the part corresponding to the lower half of the vacuum chamber, the first part made of P-type silicon
The layer is formed by selective epitaxial growth or diffusion. A second layer corresponding to a vibrating beam is selectively epitaxially grown on the surface of the first layer with n-type silicon so as to close a required portion.

A third layer corresponding to the upper half of the vacuum chamber is selectively epitaxially grown on the surface of the second layer by the high concentration P-type silicon which is easily etched. A fourth layer corresponding to a shell is selectively epitaxially grown on the surface of the third layer with n-type silicon. Silicon oxide or
The silicon nitride film is removed by etching, and an etching injection port is provided.

The first layer and the third layer are made porous by irradiating light and anodizing in hydrofluoric acid. The porous first and third layers are oxidized. The first layer and the third layer are removed with hydrofluoric acid. Hereinafter, detailed description will be given based on examples.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 8 are explanatory views of a manufacturing method according to an embodiment of the present invention. In the figure, the same symbols as those in FIG. 10 indicate the same functions. (A) As shown in FIG. 1, a film 201 of silicon oxide or silicon nitride is formed on a substrate 1 cut into an n-type silicon (100) plane. The required portion 202 of the film 201 is removed by photolithography.

(B) As shown in FIG. 2, etching was carried out with hydrogen chloride in a hydrogen (H ₂ ) atmosphere at 1050 ° C.,
A desired portion 202 is etched on the substrate 1 to undercut the film 201 to form a recess 203. 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.

(C) As shown in FIG. 3, hydrogen chloride gas is mixed with the source gas in a hydrogen (H ₂ ) atmosphere to carry out the selective epitaxial growth method. That is, at the temperature of 1050 ° C., the first half corresponding to the lower half of the vacuum chamber 5 is formed by the P-type silicon having the boron concentration of 10 ¹⁸ cm ⁻³ .
The epitaxial layer 204 is selectively epitaxially grown.

At a temperature of 1050.degree. C., a second epitaxial layer 205 corresponding to the vibrating beam 3 is selectively epitaxially grown on the surface of the first epitaxial layer 204 at a temperature of 1050.degree. A third epitaxial layer 206 corresponding to the upper half of the vacuum chamber 5 is selectively epitaxially grown on the surface of the second epitaxial layer 205 with P-type silicon having a boron concentration of 10 ¹⁸ cm ⁻³ . On the surface of the third epitaxial layer 206, the fourth epitaxial layer 20 corresponding to the shell 4 is made of n-type silicon.
7 is selectively epitaxially grown.

(D) As shown in FIG. 4, the film 201 of silicon oxide or silicon nitride is removed by etching with hydrofluoric acid (HF).
08 is provided. (E) As shown in FIG. 5, light 2 is generated in hydrofluoric acid 209.
11 is irradiated and anodized to make the first epitaxial growth layer 204 and the third epitaxial growth layer 206 porous.

(F) As shown in FIG. 6, the porous first epitaxial growth layer 204 and the third epitaxial growth layer 206 are oxidized. (G) As shown in FIG. 7, the first epitaxial growth layer 204 and the third epitaxial growth layer 2 are formed by hydrofluoric acid.
06 is removed. (H) As shown in FIG. 8, a nitride film 212 is formed on the outer surfaces of the substrate 1 and the fourth epitaxial growth layer 207 by the CVD method.
And the etching inlet 208 is closed.

In the above manufacturing method, the silicon oxide or silicon nitride film 201 is formed on the substrate 1 cut into the n-type silicon (100) surface. Membrane 20
The required portion 202 of No. 1 is removed by photolithography. Etching is performed with hydrogen chloride in a hydrogen (H ₂ ) atmosphere at 1050 ° C., a required portion 202 is etched on the substrate 1 to undercut the film 201, and a recess 203 is formed.

At a temperature of 1050 ° C., a boron concentration of 10
The first epitaxial layer 204 corresponding to the lower half of the vacuum chamber 5 is selectively epitaxially grown from ¹⁸ cm ⁻³ P-type silicon. At a temperature of 1050 ° C., a second epitaxial layer 205 corresponding to the vibrating beam 3 is selectively epitaxially grown on the surface of the first epitaxial layer 204 with n-type silicon so as to close the required portion 202.

A third epitaxial layer 206 corresponding to the upper half of the vacuum chamber 5 is selectively epitaxially grown on the surface of the second epitaxial layer 205 using P-type silicon having a boron concentration of 10 ¹⁸ cm ^-3 . A fourth epitaxial layer 207 corresponding to the shell 4 is selectively epitaxially grown on the surface of the third epitaxial layer 206 using n-type silicon.

The silicon oxide or silicon nitride film 201 is removed by etching with hydrofluoric acid (HF), and an etching injection port 208 is provided. Hydrofluoric acid 20
9 to irradiate light 211 to perform anodization treatment, so that the first epitaxial growth layer 204 and the third epitaxial growth layer 2 are formed.
06 is made porous.

Porous first epitaxial growth layer 2
04 and the third epitaxial growth layer 206 are oxidized. The first epitaxial growth layer 204 and the third epitaxial growth layer 206 are removed by hydrofluoric acid. A nitride film 213 is formed on the outer surfaces of the substrate 1 and the fourth epitaxial growth layer 207 by CVD, and the etching injection port 208 is closed. That is, in the step of FIG. 5, the N layers of the second and fourth epitaxial growth layers 205 and 207 are not made porous, but only the P layers of the first and third epitaxial growth layers 204 and 206 are made to be porous by irradiation with light. To do.

In the process of FIG. 6, the porous layers 204, 2
06 is oxidized 100 times faster than a single crystal bulk.

In the step shown in FIG. 7, hydrofluoric acid is much more diffused than hydrazine, and can be easily etched even from a narrow gap. Therefore, the etching processing time can be shortened and the size can be easily reduced. Figure 8
In the step of, the sealing of the vibrating beam 3 by the stress of the nitride film 213 attached to the vibrating beam 3
The required initial tension can be applied to.

As a result, (1) since the etching injection port 208 can be made small and small, the vibrating beam 3 can be made small, and the size of the entire apparatus can be reduced. (2) Since the etching process can be performed quickly, the processing time can be shortened and the manufacturing cost can be reduced. (3) It is not necessary to form an electrode on the semiconductor substrate 1 (the process is simplified). (4) There is no mixing of impurities due to electrode formation.

FIG. 9 is an explanatory view of the essential structure of an example of use of the vibrating beam of the present invention. In the figure, 3 is a vibrating beam. The vibrating beam 3 has two first oscillators 31 whose both ends are fixed to the diaphragm 3 and are arranged in parallel to each other, and a second oscillator which mechanically couples antinode portions of the vibration of the first oscillator 31 with each other. 32 and 32.

A magnet 40 applies a DC magnetic field perpendicular to the vibrating beam 3, and an AC current is applied to both ends of one of the first vibrators 31 by an input transformer 41, so that the vibrating beam 3 is magnetically and current-driven by a magnetic induction action. It is an excitation means that excites in a direction orthogonal to. The secondary side of the input transformer 41 is connected to both ends of the one first oscillator 31. Reference numeral 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 5
2 is used. The primary side of the output transformer 51 is connected to both ends of the other first oscillator 31, the secondary side is connected to the output terminal 53 via the amplifier 52, and is branched and connected to the primary side of the input transformer 41. As a whole, a positive feedback self-excited oscillation circuit is formed. The vibration of the vibrating beam 3 is detected by the vibration detecting means 50 and taken out as an output signal.

[0033]

As described above, according to the present invention, the vibrating beam provided on the silicon single crystal substrate is surrounded by the vibrating beam so that a gap is maintained around the vibrating beam. A method of manufacturing a vibrating transducer comprising a shell made of a silicon material forming a chamber, an exciting means for exciting the vibrating beam, and an exciting detecting means for detecting vibration of the vibrating beam, including the following steps. The manufacturing method of the vibrating transducer is characterized by. (A) A step of forming a silicon oxide or silicon nitride film on an n-type substrate. (B) A step of removing a required portion of the film by photolithography. (C) A step of forming a first layer of P-type silicon by selective epitaxial growth or diffusion in a portion corresponding to the lower half of the vacuum chamber. (D) A step of selectively epitaxially growing a second layer corresponding to the vibrating beam on the surface of the first layer with n-type silicon so as to close the required portion. (E) A step of selectively epitaxially growing a third layer corresponding to the upper half of the vacuum chamber on the surface of the second layer with a high concentration of P-type silicon that is easily etched. (F) A step of selectively epitaxially growing a fourth layer corresponding to the shell on the surface of the third layer with n-type silicon. (G) A step of etching and removing the silicon oxide or silicon nitride film to provide an etching injection port. (H) In hydrofluoric acid, light is irradiated to perform anodization treatment,
The step of making the first layer and the third layer porous. (I) A step of oxidizing the porous first layer and third layer. (J) A step of removing the first layer and the third layer with hydrofluoric acid.

As a result, (1) Since the etching inlet can be made small and small, the vibrating beam can be made small, and the size of the entire apparatus can be reduced. (2) Since the etching process can be performed quickly, the processing time can be shortened and the manufacturing cost can be reduced. (3) It is not necessary to form an electrode on the semiconductor substrate 1 (the process is simplified). (4) There is no mixing of impurities due to electrode formation.

Therefore, according to the present invention, it is possible to realize the manufacturing method of the vibration type transducer which can be miniaturized at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory view of a patterning process according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an etching process according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of an epitaxial growth process of one example of the present invention.

FIG. 4 is an explanatory diagram of an etching inlet etching process according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of anodizing process steps according to an example of the present invention.

FIG. 6 is an explanatory diagram of an oxidation process according to an example of the present invention.

FIG. 7 is an explanatory diagram of an etching process according to an embodiment of the present invention.

FIG. 8 is an explanatory diagram of a nitride film forming process according to an embodiment of the present invention.

FIG. 9 is an explanatory diagram of a main part configuration of a usage example of the apparatus of the present invention.

FIG. 10 is an explanatory diagram of a configuration of a conventional example that is generally used in the past.

11 is a cross-sectional view taken along the line AA of FIG.

FIG. 12 is an explanatory diagram of a patterning process of the conventional example of FIG.

FIG. 13 is an explanatory diagram of an etching process of the conventional example.

FIG. 14 is an explanatory diagram of an epitaxial growth process of the conventional example.

FIG. 15 is a drawing for explaining the film removal process of the conventional example.

16 is an explanatory diagram of an etching process of the conventional example of FIG.

FIG. 17 is an explanatory diagram of an epitaxial growth process in the conventional example of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Measuring diaphragm 3 ... Vibrating beam 4 ... Shell 5 ... Vacuum chamber 30 ... Magnet 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 ... Required location 203 ... Recessed portion 204 ... First epitaxial layer 205 ... Second epitaxial layer 206 ... Third epitaxial layer 207 ... Fourth epitaxial layer 208 ... Etching injection port 209 ... Hydrofluoric acid 211 ... Light source 212 ... Nitride film

Claims (1)

[Claims] 1. A vibrating beam provided on a silicon single crystal substrate, and a shell made of a silicon material surrounding the vibrating beam so as to maintain a gap around the vibrating beam and forming a vacuum chamber with the substrate. A method of manufacturing a vibrating transducer, comprising: an exciting unit that excites the vibrating beam; and an exciting detecting unit that detects vibration of the vibrating beam, including the following steps. .. (A) A step of forming a silicon oxide or silicon nitride film on an n-type or low-concentration P-type silicon substrate. (B) A step of removing a required portion of the film by photolithography. (C) A step of forming a first layer of P-type silicon by selective epitaxial growth or diffusion in a portion corresponding to the lower half of the vacuum chamber. (D) A step of forming a second layer corresponding to the vibrating beam by selective epitaxial growth or diffusion on the surface of the first layer with n-type silicon so as to close the required portion. (E) A step of selectively epitaxially growing a third layer corresponding to the upper half of the vacuum chamber on the surface of the second layer with a high concentration of P-type silicon which is easily etched. (F) A step of selectively epitaxially growing a fourth layer corresponding to the shell on the surface of the third layer with n-type silicon. (G) A step of etching and removing the silicon oxide or silicon nitride film to provide an etching injection port. (H) In hydrofluoric acid, light is irradiated to perform anodization treatment,
The step of making the first layer and the third layer porous. (I) A step of oxidizing the porous first layer and third layer. (J) A step of removing the first layer and the third layer with hydrofluoric acid.