JPH10185721A - Method for manufacturing semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor pressure sensor that can protect a pressure reception surface from a corrosive fluid by thickly forming a protection film on the pressure reception surface of a diaphragm part and strongly joining one surface of a glass pedestal and the other surface of a silicon substrate. SOLUTION: A manufacturing method consists of a piezoresistance formation process where piezoresistance 15 formed at the side of one surface 11 of a silicon substrate 1, a diaphragm part formation process for forming a recess 17 whose section is in trapezoid shape by performing anisotropic etching and for forming a diaphragm part 2 with a pressure reception surface 21 for receiving the pressure of a fluid to be measured, a protection film formation process where a protection film 18 for protecting the pressure reception surface 21 is formed on the pressure reception surface 21 and the other surface 12 of the silicon substrate 1, and a glass pedestal junction process for eliminating a protection film 18 on the other surface 12 and for joining one metallized surface 31 of a glass pedestal 3 where an axial hole 32 is provided in the other surface 12 while the positions of the axial hole 32 and the diaphragm part correspond to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor pressure sensor for measuring the pressure of a corrosive fluid, that is, a gas or a liquid.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a semiconductor pressure sensor of this type, there is a manufacturing method shown in FIG. In this manufacturing method, first, a piezo-resistor A1 that converts a resistance change due to pressure into an electrical signal with a P-type conductivity, and a conductive portion having a P + type conductivity and good electrical conductivity connected to the piezoresistance A1. A
2 is formed on one surface side of the silicon substrate A. Then, the etching resistant film A3 was formed on both surfaces of the silicon substrate A, and the etching resistant film A3 on the other surface was removed at the position corresponding to the piezoresistor A1, and anisotropically etched from the removed portion to have the bottom. A concave portion A4 having a trapezoidal cross section is formed, and a diaphragm portion A6 having a bottom portion as a pressure receiving surface A5 is formed.
The pressure of the fluid to be measured is received by the pressure receiving surface A5, and the fluid is bent.

Then, a protective film B made of a silicon oxide film is formed on the pressure receiving surface A5 and the other surface A7 of the silicon substrate A by using a chemical vapor deposition method, so-called CVD method, to protect the pressure receiving surface A5 of the diaphragm portion A6. . Next, one surface of the metalized pedestal C provided with the shaft hole C1 is joined to the other surface A7 of the silicon substrate A in a state where the positions of the shaft hole C1 and the diaphragm portion A6 correspond to each other.

[0004]

In the above-described conventional method of manufacturing a semiconductor pressure sensor, a protective film B for protecting a diaphragm portion A6 is formed on a pressure receiving surface A5, and a semiconductor for measuring the pressure of a corrosive fluid is measured. A pressure sensor can be manufactured.

However, the protective film B is formed on the pressure receiving surface A5 and the other surface A7 of the diaphragm portion A6, and the glass pedestal C is formed.
Film B between one surface of the silicon substrate A and the other surface A7 of the silicon substrate A
Are bonded together in a state where the protective film B is interposed.
When the film thickness of is increased, the bonding strength is deteriorated. When the film thickness is reduced, the pressure receiving surface A5 is not sufficiently protected by the protective film B, and may be corroded by the corrosive fluid.

The present invention has been made in view of the above circumstances, and an object of the present invention is to form a thick protective film on a pressure-receiving surface of a diaphragm portion to reliably protect the pressure-receiving surface from corrosive fluid, and It is another object of the present invention to provide a method of manufacturing a semiconductor pressure sensor capable of firmly joining one surface of a glass pedestal and the other surface of a silicon substrate.

[0007]

According to a first aspect of the present invention, there is provided a method for manufacturing a semiconductor pressure sensor, wherein a piezoresistor for converting a resistance change due to pressure into an electric signal is provided on one side of a silicon substrate. The piezoresistor forming step to be formed, and the etching resistant films formed on both sides of the silicon substrate are removed at positions corresponding to the piezoresistors on the other side, and anisotropic etching is performed to form a concave portion having a trapezoidal cross section, and measurement is performed. A diaphragm portion forming step of forming a diaphragm portion having a pressure receiving surface for receiving the pressure of the target fluid, and a protective film for removing the etching resistant film and protecting the pressure receiving surface of the diaphragm portion is provided on the pressure receiving surface and the silicon substrate. Forming a protective film on the other surface, removing the protective film on the other surface of the silicon substrate, and removing the metalized one surface of the glass pedestal having the shaft hole into the shaft hole; In state corresponding positions to each other of the fine diaphragm unit, which are not on the glass pedestal bonding step of bonding the other side, having configuration.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor according to the first aspect, wherein the protective film is formed by converting a gas into a plasma to deposit a film component.
It has a configuration formed by VD.

According to a third aspect of the present invention, in the method for manufacturing a semiconductor pressure sensor, the protective film is made of silicon oxide formed by heat-treating the silicon substrate.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. First, the conductivity type is N-type and one surface 11
The silicon substrate 1 having the other surface 12 is thermally oxidized to form a silicon oxide film 13, the silicon oxide film 13 is removed at a predetermined position, and boron is diffused. (A) are formed on both sides with respect to the center on the one surface 11 side of the silicon substrate 1.

Next, in a piezoresistor formation step, the silicon oxide film 13 on the one surface 11 is removed at a predetermined position connected to both conductive portions 14 and boron is diffused to thereby form a piezoresistor 15 having a P-type conductivity. Is formed on the one surface 11 side of the silicon substrate 1 and converts a resistance change due to pressure into an electric signal (a).

Next, in a diaphragm portion forming step, an etching resistant film 16 made of silicon nitride is formed on both sides 11 and 12 of the silicon substrate 11 by using a chemical vapor deposition method, so-called CVD method, and a resistive film on the other surface 12 side is formed. The removed portion is formed by removing the etching film 16 at a position corresponding to the piezoresistor 15 by ordinary photolithography or etching. Using the etching resistant film 16 as a mask, anisotropic etching is performed from the removed portion with a KOH solution,
A concave portion 17 having a trapezoidal cross section having a width narrower toward one side is formed, and a diaphragm portion 2 having a bottom portion of the concave portion 17 as a pressure receiving surface 21 is formed, and a pressure of a fluid to be measured is applied to the pressure receiving surface 21. (B). Then, the silicon oxide film 13 and the etching resistant film 16 on the other surface 12 side of the silicon substrate 1 are removed.

Next, in a protective film forming step, the pressure-receiving surface 21 of the diaphragm portion 2 and the protective film 18 made of silicon oxide are formed to have a thickness of 1 μm by plasma CVD in which a gas is turned into a plasma to deposit a film component. It is formed on the other surface 12 to protect the pressure receiving surface 21 (c).

Next, in the glass pedestal 3 joining step,
Protective film 18 formed on pressure receiving surface 21 of diaphragm 2
A resist film 18a having etching resistance is applied to the surface, and then etched to form a protective film 18 formed on the pressure receiving surface 21.
Is removed, the protective film 18 formed on the other surface 12 of the silicon substrate 1 is removed (d).

Here, the glass pedestal 3 having one surface 31
Has a shaft hole 32 made of Pyrex glass, and one surface 31 is metallized with metal. In a state where the shaft hole 32 and the diaphragm portion 2 correspond to each other, the one surface 31 is formed by anodic bonding by applying a high DC voltage and bonding.
Are joined directly to the other surface 12 of the silicon substrate 1 without the intermediary of the protective film 18, and each is firmly joined (e).

The operation of this will be described. The fluid to be measured has corrosive properties such as gasoline vapor, and the glass base 3
Is bonded to the other surface 12 of the silicon substrate 1, so that the one surface 31 is introduced into the shaft hole 32 of the glass pedestal 3 with pressure without leakage, and the pressure receiving surface 21 of the diaphragm 2 is
Receives the pressure of the fluid. When the pressure of the fluid is applied to the pressure receiving surface 21, the diaphragm 2 bends in proportion to the difference between the pressure of the fluid and the atmospheric pressure. The resistance value changes in proportion to the magnitude of the deflection, and the resistance value is output as an electric signal to a terminal (not shown) via the conductive portion 14.
Measure the pressure of the fluid. Here, the diaphragm section 2
Protective film 18 is 1 micrometer thick and pressure receiving surface 2
1, the pressure receiving surface 21 is protected by the thick protective film 18, so that the diaphragm portion is not corroded even if the fluid to be measured is corrosive.

In the method of manufacturing a semiconductor pressure sensor according to one embodiment, as described above, the diaphragm 2
Pressure-receiving surface 21 and the other surface 12 of silicon substrate 1
8, the protective film 18 on the other surface 12 is removed in a state where only the pressure receiving surface 21 is left, and one surface 31 of the glass pedestal 3 and the other surface 1
Therefore, the pressure receiving surface 21 is protected by the thick protective film 18 and is corroded even by a corrosive fluid. The pressure of the fluid can be measured without the need, and since the protective film 18 is not interposed between the one surface 31 of the glass pedestal 3 and the other surface 12 of the silicon substrate 1, a semiconductor pressure sensor that can firmly join each of them can be stably formed. Can be manufactured.

Further, since the protective film 18 is formed by plasma CVD in which the gas is turned into plasma and the film components are deposited, the piezoresistor 15 is not affected by heat in the protective film forming step, and the protective film 18 is not at a high temperature. A semiconductor pressure sensor that is formed at a low temperature close to room temperature and can accurately measure the pressure of a fluid can be manufactured.

In this embodiment, the protective film 18 made of silicon oxide is formed by plasma CVD in which a gas is formed into plasma to deposit film components. However, when the protective film 18 having a high density without voids is required. In the method, the silicon substrate 1 may be heat-treated at a predetermined temperature to form the protective film 18 made of silicon oxide on the pressure receiving surface 21 and the other surface 12 of the diaphragm 2, and the method is not limited.

In this embodiment, the protective film 18 is made of silicon oxide. However, the protective film 18 may be made of silicon nitride obtained by using, for example, plasma CVD, and is not limited.

[0021]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor, wherein a protective film is formed on a pressure receiving surface of a diaphragm portion and the other surface of a silicon substrate, and the other protective film is removed while only the pressure receiving surface is left. Then, since one surface and the other surface of the glass pedestal are joined to each other, a thick protective film is formed, and the pressure receiving surface is protected by the thick protective film. It is possible to measure the pressure of the fluid without being clogged, and to stably manufacture a semiconductor pressure sensor that can firmly join each other because the protective film is not interposed between one surface of the glass pedestal and the other surface of the silicon substrate. Can be.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor. In addition to the effect of the first aspect, a plasma CV in which a protective film converts a gas into a plasma and deposits a film component.
A semiconductor pressure sensor capable of measuring the pressure of a fluid accurately without forming a protective film at a low temperature close to a room temperature, not at a high temperature, without piezoresistance being thermally affected in the protective film forming step. Can be manufactured.

According to the third aspect of the present invention, in addition to the effect of the first aspect, the diaphragm portion is formed by heat-treating the silicon substrate. The pressure receiving surface is protected by a protective film made of silicon oxide having a density close to the true density, the corrosion resistance of the pressure receiving surface is further improved, and a semiconductor pressure sensor capable of reliably measuring the pressure of a corrosive fluid can be manufactured. .

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a semiconductor pressure sensor showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor pressure sensor showing a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 silicon substrate 11 one surface 12 other surface 15 piezoresistive 16 etching resistant film 17 concave portion 18 protective film 2 diaphragm 21 pressure receiving surface 3 glass pedestal 31 one surface 32 axial hole

Claims (3)

[Claims] 1. A piezoresistor forming step in which a piezoresistor for converting a resistance change due to pressure into an electric signal is formed on one surface of a silicon substrate, and an etching resistant film formed on both surfaces of the silicon substrate is formed on the other surface by a piezoresistor. Removing at a position corresponding to the resistance, performing anisotropic etching to form a trapezoidal concave section, and forming a diaphragm having a pressure receiving surface for receiving the pressure of the fluid to be measured; Removing the etching film, forming a protective film on the pressure receiving surface and the other surface of the silicon substrate to form a protective film for protecting the pressure receiving surface of the diaphragm; removing the protective film on the other surface of the silicon substrate; A glass pedestal joining step of joining one of the metalized surfaces of the glass pedestal provided with the glass pedestal to the other surface in a state where the axial hole and the diaphragm portion correspond to each other. A method of manufacturing a semiconductor pressure sensor. 2. The method for manufacturing a semiconductor pressure sensor according to claim 1, wherein said protective film is formed by plasma CVD in which a gas is turned into plasma and a film component is deposited. 3. The method according to claim 1, wherein the protective film is a silicon oxide formed by heat-treating the silicon substrate.