JPH02123769A - Manufacture of diaphragm for semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To form the desired thickness of a diaphragm with excellent accuracy by bonding an Si substrate, to which a high-concentration impurity layer is shaped, and using the whole as an etching stopper while polishing one surface. CONSTITUTION:The high-concentration impurity layers 2, 2' of boron are formed onto both surfaces of an Si single crystal substrate 1. The Si substrate, surfaces of which are washed and to which hydrophilic properties are imparted, and an Si substrate 3, surfaces of which have (100) faces or (110) faces, are superposed directly in a clean atmosphere at room temperature, and heated and bonded. One surface of the Si substrate 1 cemented is mirror-polished 1' until thickness thereof is brought to thickness acquired by adding the thickness of the substrate 3 and the desired thickness of a diaphragm. The protective film 4 of a region 5 in which the diaphragm is shaped is removed through photoetching treatment, and a diaphragm 5' is formed through anisotropic etching. Accordingly, the silicon-diaphragm can be shaped uniformly with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of silicon diaphragms for semiconductor pressure sensors.

A conventional method for manufacturing a diaphragm will be briefly explained. A protective film is formed on an S substrate having a (100) or (110) surface. The protective film is made of various materials such as S10, S, and N. The protective film in the area where the diaphragm will be formed is removed by photoetching, and the diaphragm is formed by anisotropic etching using an alkaline etching solution. However, as the diameter of the S1 wafer increases, the thickness of the S1 wafer increases and the etching depth for forming the diaphragm increases, making it difficult to obtain a highly accurate and uniform diaphragm thickness. There were some drawbacks.

The purpose of the present invention is to control the thickness accuracy and uniformity of the diaphragm by bonding an S substrate on which a high concentration impurity layer is formed and using it as an etching stopper, and at the same time polishing one side to obtain the desired diaphragm thickness. It is formed with high precision and reduces variations in characteristics as a pressure sensor.

The present invention will be explained according to the drawings. FIGS. 1(a) to 1(f) show process diagrams for manufacturing a silicon diaphragm according to the manufacturing method of the present invention.

(a) 1 is an S1 crystal substrate.

(b) S, 10 high boron concentration layers on both sides of the single crystal substrate 1
A high-temperature treatment at 00° C. or higher is performed to diffuse boron into the substrate so that a highly concentrated impurity layer 2.2' of >10 cm is formed to a thickness of several μm.

(c) The S substrate of (b) whose surface has been cleaned and made wood-friendly, and the S substrate whose surface has a (100) plane or a (110) plane.
, the substrates 3 are directly stacked together in a clean atmosphere at room temperature. This closely attached S1 wafer is heated and bonded in an N2 or 02 atmosphere at 100.0° C. or higher.

(d) One side of the bonded 81 substrate 1 is mirror polished 1' to a thickness equal to the thickness of the substrate 3 plus the desired diaphragm thickness.

(e) A protective film 4.4' is formed in the same manner as in the conventional diaphragm forming method. The protective film is a 5102 film, S, or N film formed by CVD, sputtering, thermal oxidation, or the like. The protective film in the region 5 where the diaphragm will be formed is removed by photoetching.

(f') Using an alkaline etching solution (111)
The diaphragm 5' is formed by anisotropic etching which takes advantage of the fact that the etching speed of the plane is extremely slow compared to the (100) and (110) planes.

[Example] A high boron concentration layer of >1 O"cm-" was formed on an n-type S1 single crystal substrate by high-temperature treatment at 1060° C. for 60 minutes. Furthermore, after cleaning this S1 single crystal substrate, the crystal orientation was adjusted (
The S having a 100) surface was stacked on the substrate and bonded by heat treatment for 60 minutes in a N2 atmosphere at 1050°C. CV
1000 81N films were formed by the D method. After patterning the diaphragm region by photo-etching and removing the S and N films, 2 mo1 of KO was applied at 80°C.
Etching treatment was performed using H solution. Etching speed is S,
It is 0.4 μm/min for the N film, 1.4 μm/mjn for the (100) plane of s:, and
In the case of -1 boron high concentration layer, the diaphragm thickness was 160±2 using the fact that the etching rate was 1/20 and the etching rate suddenly slowed down.
Diaphragms with high μm uniformity can be formed with high precision.
It was possible to reduce the variation in sensitivity characteristics as a pressure sensor to less than ±10%. The biggest factor that determines the variation in sensitivity of pressure sensors is the shape of the diaphragm. Therefore, according to the present invention, a silicon diaphragm can be manufactured uniformly and with high precision, so that variations in the characteristics as a pressure sensor can be extremely reduced, which has a great practical effect.

[Brief explanation of the drawing]

Figure 1 (a), (b), (c), (d), (e), (f
) is a process diagram showing a method for manufacturing a silicon diaphragm according to the present invention. In the figure, 1 is a silicon (Sl) single crystal substrate, 2.2' is a high concentration impurity layer, and 3 is (100) or (11).
0) side silicon substrate, 4.4' is a protective film, 5 is a diaphragm region, and 5' is a diaphragm.

Claims (1)

[Claims] (a) A step of bonding a silicon substrate (first) having a high concentration impurity layer and a silicon substrate (second) having a (100) plane or a (110) plane; Silicon substrate with a concentrated impurity layer (first
); and (c) anisotropically etching the silicon substrate (second) using the high concentration impurity layer as an etching stopper. diaphragm manufacturing method.