JPH0521814A - Pressure sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To facilitate the manufacture and get stable property, using a cheap constituent material. CONSTITUTION:A thick glass film 2 is made on a silicon substrate 1 provided with an protective film 3 against etching, and the silicon substrate 1 (figure A) is anisotropically etched to provide an etched part 4, and a diaphragm 2a of the thick glass film 3 is made. In the figure B, a silicon film 5 is deposited onto the top of the thick glass film 2. In the figure C, ions are implanted into the silicon film 5 to form a piezo effect region 7, and then an insulating layer is made of an insulating film 6 (figure C), and an electrode 8 is provided in the piezo effect region 7 (figure E).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor utilizing the piezo effect, and more specifically, a diaphragm pressure in which a semiconductor region having a piezo effect (resistivity) is formed on the glass thick film as a pressure receiving portion. Regarding sensors.

[0002]

2. Description of the Related Art Since a diaphragm type pressure sensor in which a silicon diaphragm is used as a pressure receiving portion and a piezoresistive element is formed on the silicon diaphragm is small and has high sensitivity,
In recent years, it has been used in fields such as automobile electronics, industrial measurement, medical fees and household appliances. In particular, the connection with a microcomputer greatly improves the function and expands the application field, and accordingly, a highly accurate, highly reliable, and inexpensive pressure sensor is required. As a silicon diaphragm type pressure sensor, n of plane orientation (100)
Type silicon substrate is thinned by anisotropic etching at the four sides on a square diaphragm to form a P-type piezoresistive element whose longitudinal direction is parallel to the <110> crystal axis by boron ion implantation. Many things are commercially available.

The sensitivity of the semiconductor diaphragm type pressure sensor formed as described above is 2 of the ratio of the piezoresistive coefficient determined by the crystal axis of silicon to the side length and thickness of the diaphragm.
It changes in proportion to the square. Of these, the piezoresistance coefficient is a constant if the crystal axis is fixed, so the sensitivity of the pressure sensor is
It is defined by the dimensions of the diaphragm, in particular the thickness and the uniformity of the thickness. Therefore, in order to obtain a semiconductor diaphragm type pressure sensor having uniform sensitivity and excellent linear ratio, it has been a technical subject to make the thickness of the diaphragm uniform. However, conventionally, since the flatness of the etching surface is likely to vary and the yield is low, many proposals have been made for high yield production.

As a known document relating to the present invention, there is a "method for manufacturing a pressure sensor" in JP-A-59-172778. The process of the "pressure sensor manufacturing method" will be described with reference to FIG. 2A to 2E are views for explaining the manufacturing process of the conventional pressure sensor.
1 is a silicon substrate, 12 is an oxide single crystal thin film, 13 is a silicon single crystal thin film, 14 is a resistance region, 15 is an etching protective film, 16 is an insulating film, and 17 is an electrode.

FIG. 2A is a step of sequentially epitaxially growing an oxide single crystal thin film 12 and a silicon single crystal thin film 13 on a silicon substrate 11, and FIG. 2B is a step of forming a resistance region 14 on the silicon single crystal thin film 13. 2C, the etching protection film 15 made of silicon nitride (Si ₃ N ₄ ) or the like is formed on both surfaces of the substrate except the portion where the diaphragm is formed. In the step of FIG. 2D, the silicon substrate 11 portion is etched. At this time, since the oxide single crystal thin film 12 is not etched by the etchant, the silicon substrate 11 is etched but the oxide single crystal thin film 1 is etched.
Stop when you reach 2. FIG. 2E shows the final step, and the silicon diaphragm pressure sensor is obtained by forming the insulating film 16 and the electrode 17.

In the silicon diaphragm type pressure sensor manufactured by the above process, as shown in the process of FIG. 2A, the silicon single crystal thin film 13 is formed on the oxide single crystal thin film 12 for stopping the etching. The method is very expensive. In the above method, the silicon single crystal thin film 13 is deposited by the CVD (Chemical Vapor Desition) method or the sputtering method.
3 is a diaphragm, and it takes a long time to obtain the required thickness. Also, two oxide thin films 12
There is a method in which the silicon single crystal substrate 11 on which is formed is bonded so that the oxide thin film 12 faces it, and then one silicon substrate 11 is polished to a predetermined thickness. However, the polishing process is inefficient and the abrasive product is expensive.

[0007]

[Purpose] The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a simple and inexpensive diaphragm type pressure sensor.

[0008]

In order to achieve the above object, the present invention provides (1)
A silicon substrate, a glass thick film formed on the silicon substrate, and a silicon thin film formed on the glass thick film,
A pressure receiving part which is composed of a piezo effect region formed in a predetermined range on the silicon thin film and a lead wire connected to the piezo effect region, and which has a glass thick film corresponding to the predetermined range of the silicon thin film without the silicon substrate. Further, (2) a step of forming a glass thick film on the silicon substrate, and a step of removing the central portion of the silicon substrate by etching to form a diaphragm of the glass thick film,
A step of forming a silicon thin film on the glass thick film; a step of forming a piezo effect region at a predetermined position of the diaphragm part of the glass thick film of the silicon thin film; and a part of the piezo effect region being insulated to form a lead wire. And a step of forming. Hereinafter, description will be given based on examples of the present invention.

1 (a) to 1 (e) are views for explaining one embodiment of the pressure sensor and the manufacturing method of the present invention.
1A is a step of forming a glass thick film on a silicon substrate, FIG. 1B is a step of forming a diaphragm made of a glass thick film, and FIG. 1C is a step of forming a silicon thin film on the glass thick film. 1 (d) is a diagram for explaining a step of forming a piezo effect region in a silicon thin film, and FIG. 1 (e) is a diagram for explaining a step of forming an electrode. 1 is a silicon substrate, 2 is a glass thick film, and 3 is a glass thick film. Is an etching protection film, 4 is an etching part,
5 is a silicon thin film, 6 is an insulating film, 7 is a piezo effect region,
8 is an electrode.

In the step of forming a glass thick film on a silicon substrate of FIG. 1A, a glass having a thermal expansion coefficient substantially equal to that of the silicon substrate 1 is formed on an n-type silicon substrate 1 having a plane orientation (100). For example, Pyrex 30μm
A thick film having a thickness of (micrometer) is formed. Specifically, film formation is performed by a screen printing method or a sol-gel method. In the screen printing method, a fine mesh screen is arranged on the silicon substrate 1 at a constant interval corresponding to a thickness slightly larger than a target glass thick film, and Pyrex fine particles are arranged on the screen. The viscous body obtained by mixing the frit glass as described above with an organic binder is placed, and the placed viscous body is pressed on the screen with a squeegee or the like so that the viscous body has a constant thickness, and the screen is removed. As a result, the viscous material is applied with a constant thickness on the silicon substrate 1. The uniformly applied viscous substance is heated at about 300 ° C. to blow off the organic binder. Then, the frit glass is melted at a temperature of about 1200 ° C. to form the thick glass film 2 on the silicon substrate 1.

The sol-gel method is originally a method of solidifying a solution of a metal organic and inorganic compound as a gel and preparing an oxide solid by heating the gel. The solution is decomposed and polymerized to form a sol in which fine particles of metal oxides or hydroxides are dissolved, and the reaction is further promoted to gel, and the resulting porous gel is heated to form amorphous, glass, or polycrystals. I was able to make it.

For example, tetraoxide silane nSi (O
By heating in a C ₂ H ₅ ) ₄ aqueous solution and ethyl alcohol C ₂ H ₅ OH and hydrochloric acid HCl, hydrolysis and polycondensation reaction proceed to generate an alkoxide molecule.
A sol of iO ₂ (silicon oxide) is obtained. 2 more of the gel
A gel body of the pseudo-collection particles is formed by heating and reacting at 5 to 80 ° C., and the pseudo-collection particles are dried to form a dry gel body.
It is heated at ˜900 ° C. to form a thick film of silicon glass and formed.

In the step of forming the diaphragm made of the thick glass film of FIG. 1B, the silicon substrate 1 is etched at an etching angle of 54.7 ° except for the etching protection film 3 of silicon nitride (Si ₃ N ₄ ). Although it is anisotropically etched with a constant taper, the etching is stopped by the glass thick film 2 to form a diaphragm by the glass thick film 2. Next, a silicon thin film 5 is formed on the surface of the glass thick film 2 by CVD or sputtering (FIG. 1 (c)). Further, ions such as boron are implanted into the silicon thin film 5 to form a piezo effect region 7 including a piezo effect element group which is a P-type semiconductor, and an insulating film 6 of SiO ₂ is further formed. Then, the piezoelectric effect region 7 is insulated (FIG. 1D). An electrode 8 made of aluminum or the like is connected to the piezoelectric effect region 7 (FIG. 1E), and the glass thick film 2 is formed.
A pressure sensor having a pressure receiving diaphragm is completed.

[0014]

As apparent from the above description, according to the present invention, an inexpensive glass thick film of Pyrex or the like having a thermal expansion coefficient substantially equal to that of the silicon substrate is formed on the silicon substrate, and the back surface of the silicon substrate is By anisotropic etching, only the thick glass film remains and becomes the pressure receiving surface.
The thick glass film can be easily made uniform by heat treatment, so that the pressure receiving property becomes constant. Therefore, by detecting the strain due to the pressure application of the glass thick film in the piezo effect region of the Si body, a pressure sensor that is significantly cheaper than the conventional diaphragm type semiconductor pressure sensor having an expensive silicon pressure plate is provided. be able to.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of a pressure sensor and a manufacturing method of the present invention.

FIG. 2 is a diagram for explaining a manufacturing process of a conventional pressure sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Glass thick film, 3 ... Etching protective film, 4 ... Etching part, 5 ... Silicon thin film, 6 ... Insulating film, 7 ... Piezo effect region, 8 ... Electrode.

Claims (2)

[Claims] 1. A silicon substrate, a glass thick film formed on the silicon substrate, a silicon thin film formed on the glass thick film, a piezo effect region formed in a predetermined range on the silicon thin film, and A pressure sensor comprising: a lead wire connected to the piezo effect region; and a thick glass film corresponding to a predetermined range of the silicon thin film as a pressure receiving portion having no silicon substrate. 2. A step of forming a glass thick film on a silicon substrate, a step of removing a central portion of the silicon substrate by etching to form a diaphragm of the glass thick film, and a silicon thin film on the glass thick film. A step of forming a piezo effect region at a predetermined position of a diaphragm portion of the glass thin film of the silicon thin film, and a step of forming a lead wire by insulating a part of the piezo effect region. A method of manufacturing a pressure sensor, comprising: