JPH1074957A - Manufacture of semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor pressure sensor in which down-sizing is enabled while in a state where a diaphragm part with a specified thickness and length is formed and a joint surface between a glass base and the diaphragm part. SOLUTION: An etching resistance film 14 is formed on both surfaces of a silicon substrate 1 (step for forming an etching resistance film), and it is also formed on both surfaces of a supporting substrate 2 for supporting the substrate 1, the film 14 on at least one surface 21 side thereof is removed at a specified position to form an opening part 23a, and anisotropic etching is applied from the opening part 23a to form a through-hole 25 (step for forming a through hole). Further, one surface 11 of the substrate 1 is adhered to one surface 21 of the substrate 2 (adhesion step), and anisotropic etching is applied from the other surface 22 of the substrate 2 to form a diaphragm part 15 on the substrate 1 (step for forming a diaphragm part).

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 gas or 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, a piezoresistor A for converting a resistance change due to pressure into an electric signal is formed on one side, and a silicon nitride film is formed on both sides of a silicon substrate B having a thickness of 400 μm via a silicon oxide film B1. An etching resistant film B2 is formed. Then, the etching resistant film B2 on the other side is removed at a predetermined position to provide an opening (a).

Next, a trapezoidal etched portion B3 is formed by anisotropic etching using a KOH solution from the opening, and a diaphragm portion B4 which bends in response to pressure has a predetermined thickness of 20 μm and a thickness of 1 mm. And is formed on the silicon substrate B at a position corresponding to the piezoresistor A (b).

The glass pedestal C having the shaft hole C1 formed by removing the etching resistant films B2 on both sides of the silicon substrate B is placed on the silicon substrate B with the respective positions of the shaft hole C1 and the diaphragm B4 corresponding to each other. Bonding surface B5 which is the other surface of
(C). Next, a metal made of Al is sputtered to form a wiring portion A1 connected to the piezoresistor (d).

More specifically, a glass pedestal C is required to be mounted on a package to be mounted, and a bonding surface B5 of the silicon substrate B is required to secure the bonding strength between the glass pedestal C and the silicon substrate B. Has a predetermined area. Further, the silicon substrate B has a coefficient of thermal expansion of a glass pedestal C.
Therefore, when they are joined at the joining surface B5, stress is generated due to the difference in the coefficient of thermal expansion and the stress is relieved. In addition, the etching is anisotropic etching, and the etched portion B3 is formed in a trapezoidal shape that is wider toward the opening.

[0006]

In the above-described conventional method of manufacturing a semiconductor pressure sensor, a diaphragm portion B4 which bends in accordance with a pressure applied is formed on a silicon substrate B.
A semiconductor pressure sensor for measuring pressure can be manufactured.

However, when the diaphragm portion B4 is formed to have a predetermined thickness and a predetermined length, the silicon substrate B has a trapezoidal shape in which the etching portion B3 is formed in a trapezoidal shape that is wider on the opening side, that is, on the other surface side. Since the joint surface B5 with the pedestal C must be ensured, the size in the substrate surface direction, that is, the direction perpendicular to the thickness direction is 4 mm.
There was a problem that the size was increased to.

The present invention has been made in view of the above problems, and has as its object to form a diaphragm portion having a predetermined thickness and a predetermined length and to secure a joint surface with a glass pedestal. Accordingly, it is an object of the present invention to provide a method of manufacturing a semiconductor pressure sensor that can achieve miniaturization in a substrate surface direction.

[0009]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor, comprising the steps of: forming an etching resistant film on both surfaces of a silicon substrate; An etching resistant film is formed on both surfaces of a supporting silicon substrate that supports the substrate, and at least one side of the etching resistant film is removed at a predetermined position to provide an opening, and anisotropic etching is performed from the opening to reach the other surface. A through hole forming step of forming a trapezoidal etched portion wider on the opening side and removing the etching resistant film on both sides to form a through hole; and forming one side of the silicon substrate and one side of the supporting silicon substrate. A bonding step of bonding each other with the respective substrate surfaces exposed,
Anisotropic etching from the other side of the supporting silicon substrate,
A diaphragm portion forming step of forming a diaphragm portion having a predetermined thickness and a predetermined length that bends in response to the applied pressure on the silicon substrate; removing the etching resistant film on the other surface side of the silicon substrate; A piezoresistor forming step of forming a piezoresistor for converting a change into an electric signal at a position corresponding to the diaphragm portion, and a glass pedestal provided with a shaft hole, in a state where the positions of the shaft hole and the diaphragm portion correspond to each other,
And a glass pedestal joining step of joining the other surface of the supporting silicon substrate as a joining surface.

According to a second aspect of the present invention, in the method for manufacturing a semiconductor pressure sensor according to the first aspect, the step of forming the through-hole includes removing the etching-resistant film on both sides at the predetermined position. And the anisotropic etching is performed from both the openings to form the etching portions communicating with each other to form the through holes.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG.

The silicon substrate 1 is made of a flat silicon wafer having a thickness of 200 μm, and has one surface 11.
And the other surface 12, and a silicon oxide film 13 is provided on both surfaces. First, in an etching-resistant film forming step, the etching-resistant film 14 made of a silicon nitride film is
3 on both surfaces (a).

The supporting silicon substrate 2 is made of a flat silicon wafer having a thickness of 200 μm,
1 and the other surface 22 to support the silicon substrate 1. In the through-hole forming step, after the etching resistant film 23 made of a silicon nitride film is formed on both sides, the etching resistant film 23 is removed at a predetermined position on the surface 21 by ordinary photolithography and etching, and the opening is formed. A portion 23a is formed.

Using the etching resistant film 23 as a mask, KOH
An etching portion 24 is formed by anisotropic etching from the opening portion 23a with the solution, and etching is performed until the width of the etching portion 24 on the one surface 21 side becomes a length for forming a later-described diaphragm portion 15 having a predetermined length. As a result, a trapezoidal etching portion 24 having a wider width as it reaches the other surface 22 of the supporting silicon substrate 2 and approaches the opening 23a is obtained (b). Then, the through-hole 25 is formed by removing the etching resistant film 23 on both sides (c).

Next, in a bonding step, the etching resistant film 14 on the one surface 11 side of the silicon substrate 1 is
The silicon oxide film 13 is removed by HF solution by plasma etching. With the respective substrate surfaces exposed and facing each other, the one surface 11 of the silicon substrate 1 and the one surface 21 of the supporting silicon substrate 2 are heat-treated at approximately 1100 degrees Celsius and bonded together (c).

Next, in a diaphragm portion forming step, the other surface 22 of the supporting silicon substrate 2 is exposed to KOH solution.
From the side, the anisotropic etching is performed until the thickness becomes 20 μm, which is the predetermined thickness, and the diaphragm portion 15 having the predetermined length of 1 mm and flexing in response to the applied pressure is formed on the silicon substrate 1. (D).

Next, in a piezoresistor forming step, the etching resistant film 14 on the other surface 12 side of the silicon substrate 1 is removed, and a piezoresistor 3 for converting a resistance change due to pressure into an electric signal is formed at a position corresponding to the diaphragm portion 15. And Al
(E) is formed by sputtering a metal consisting of

Next, in a glass pedestal joining step, a glass pedestal 4 having a thickness of 1 mm provided with a shaft
The other surface 22 of the supporting silicon substrate 2 is joined as a joining surface 26 in a state where the positions of the diaphragm 1 and the diaphragm portion 15 correspond to each other (f).

The operation of the above will be described. The gas or liquid fluid is introduced into the shaft hole 41 of the glass pedestal 4 with pressure. When the pressure of the fluid is applied, the diaphragm 15 bends in proportion to the difference between the pressure of the fluid and the atmospheric pressure, and the resistance value of the piezoresistor 3 formed in the diaphragm 15 is proportional to the magnitude of the bend. The resistance value is output to a terminal (not shown) as an electric signal to measure the pressure of the fluid.

In the method of manufacturing the semiconductor pressure sensor according to the first embodiment, as described above, the silicon substrate 1
In a state where one surface 11 of the support silicon substrate 2 and the one surface 21 of the support silicon substrate 2 where the width of the formed through hole 25 is wide are bonded together, Since the diaphragm portion 15 having a predetermined thickness and a predetermined length is formed on the silicon substrate 1 by the reactive etching, the glass pedestal 4 is formed on the glass pedestal 4 in comparison with the conventional method in which the diaphragm portion is formed without bonding the supporting silicon substrate 2. The bonding surface 26 of the supporting silicon substrate 2 to be bonded is widened, and a semiconductor pressure sensor whose size in the substrate surface direction is reduced to 2.5 mm can be manufactured.

A second embodiment of the present invention will be described below with reference to FIG. In the second embodiment, a manufacturing process different from that of the first embodiment will be described, and members having substantially the same functions as those of the first embodiment are denoted by the same reference numerals.

The supporting silicon substrate 2 is made of a flat silicon wafer having a thickness of 400 μm.
1 and the other surface 22 to support the silicon substrate 1. In the through hole forming step, after the etching resistant film 23 made of a silicon nitride film is formed on both sides, the etching resistant film 23 is removed at a predetermined position on both sides by ordinary photolithography and etching. An opening 23a is formed.

Using the etching resistant film 23 as a mask, KOH
Anisotropic etching is performed from both openings 23a with a solution to form trapezoidal etched portions 24 on both sides,
Etching is performed until the width of the etched portion 24 on the side becomes a length that forms the diaphragm portion 15 having a predetermined length, and the etched portion 24 on both sides is connected, that is, the etched portion 24 that reaches the other surface 22 is formed, A through hole 25 is formed (b). After that, the etching resistant film 14 on both sides is removed (c).

In the method of manufacturing a semiconductor pressure sensor according to the second embodiment, as described above, the etching resistant films 23 on both sides at predetermined positions are removed in the through hole forming step to provide both openings 23a. Since the through-holes were formed by anisotropic etching from both the openings 23a, the supporting silicon substrate 2 having a thickness twice that of the supporting silicon substrate 2 was etched in the same time for etching only from the one surface 21 side, and the bonded glass pedestal 4 was formed. It is possible to manufacture a semiconductor pressure sensor in which the stress caused by the difference in the coefficient of thermal expansion between the support silicon substrate 2 and the support silicon substrate 2 is mitigated by the thick support silicon substrate 2 and cracks generated in the support silicon substrate 2 or the silicon substrate 1 are prevented. it can.

[0025]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor pressure sensor, comprising: bonding one surface of a silicon substrate to one surface of a supporting silicon substrate having a wide formed through hole; Since the diaphragm portion having a predetermined thickness and a predetermined length was formed on the silicon substrate by anisotropic etching from the other surface side of the supporting silicon substrate having a small width, the diaphragm portion was formed without bonding the supporting silicon substrate. Compared with the related art, the bonding surface of the supporting silicon substrate bonded to the glass pedestal becomes wider, and a semiconductor pressure sensor whose size in the substrate surface direction is reduced can be manufactured.

According to a second aspect of the present invention, in addition to the effect of the first aspect, in the through hole forming step, the etching resistant films on both sides at predetermined positions are removed, and both openings are formed. Since the through-hole was formed by anisotropic etching from both openings, the supporting silicon substrate having a thickness twice that of the supporting silicon substrate was etched in the same time to etch only from one side, and the glass pedestal and the support were joined. The stress caused by the difference in the coefficient of thermal expansion from the silicon substrate is alleviated by the thick supporting silicon substrate, and a semiconductor pressure sensor in which cracks generated in the supporting silicon substrate or the silicon substrate are prevented can be manufactured.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram showing a first embodiment of the present invention.

FIG. 2 is a manufacturing process diagram showing a second embodiment of the present invention.

FIG. 3 is a manufacturing process diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 1 silicon substrate 11 one surface 12 other surface 14 etching resistant film 15 diaphragm portion 2 supporting silicon substrate 21 one surface 22 other surface 23 etching resistant film 23a opening 24 etching portion 25 through hole 26 bonding surface 3 piezo resistance 4 glass pedestal 41 shaft hole

Claims (2)

[Claims] An etching-resistant film forming step of forming an etching-resistant film on both surfaces of a silicon substrate; forming an etching-resistant film on both surfaces of a supporting silicon substrate supporting the silicon substrate; An opening is provided at the position and an anisotropic etching is performed from the opening to form a trapezoidal etched portion that reaches the other surface and is wider toward the opening, and the etching resistant films on both sides are removed. A through-hole forming step of forming a through-hole, and forming one side of the silicon substrate and one side of the supporting silicon substrate,
A bonding step of bonding each other with the respective substrate surfaces exposed, and anisotropic etching from the other surface side of the supporting silicon substrate,
A diaphragm portion forming step of forming a diaphragm portion having a predetermined thickness and a predetermined length on the silicon substrate, the diaphragm portion having a predetermined thickness and a predetermined length that bends in response to the applied pressure; A piezoresistor forming step of forming a piezoresistor for converting a change into an electric signal at a position corresponding to the diaphragm portion; and A glass pedestal joining step of joining the other surface as a joining surface. 2. The through-hole forming step includes removing the etching-resistant film on both sides at the predetermined position to provide both openings, and performing anisotropic etching from both openings to communicate with each other. The method according to claim 1, wherein the through hole is formed by forming the etching portion.