JPH07169659A - Method of joining semiconductor wafer - Google Patents

Abstract

PURPOSE:To provide a method of joining semiconductor wafers together which enables direct joining of semiconductor wafers without interposing foreign matters. CONSTITUTION:The surfaces of two semiconductor wafers are mirror-polished, at least one of the polished surfaces is treated by hydrofluoric acid solution and washed by water, the polished surfaces of the two semiconductor wafers are joined mutually under clean conditions and thereafter they are heated. Semiconductor wafers are joined in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining semiconductor wafers such as silicon.

[0002]

2. Description of the Related Art Various methods are known as techniques for forming another semiconductor layer of the same type or different in composition and impurity concentration on the surface of a semiconductor wafer. For example, there are a vapor phase growth method applying a chemical vapor deposition method or a physical vapor deposition method, a liquid phase epitaxial growth method, an alloy joining method, an adhesion method using an adhesive layer such as solder. However, various conventional vapor deposition methods have a problem that the deposition rate is slow, and it takes an extremely long time to form a semiconductor layer having a thickness of, for example, several 100 μm. Further, the method of joining the semiconductor wafers with the adhesive layers of different materials has the disadvantages that the adhesive layer material diffuses into the semiconductor when heated and the compound is generated to cause alteration.

[0003]

As described above, the conventional various vapor deposition methods have a problem that it takes a long time to deposit a thick semiconductor layer, and the method of joining semiconductor wafers with an adhesive layer made of a different material has the following problems. There is a problem that the adhesive layer material is deteriorated.

In order to solve the above problems, it is an object of the present invention to provide a method for bonding semiconductor wafers, which allows semiconductor wafers to be directly bonded to each other without the presence of foreign matter.

[0005]

According to the present invention for solving the above problems, the surfaces of two semiconductor wafers are mirror-polished, and at least one of the polished surfaces is treated with a hydrofluoric acid-based solution. It is a method of joining semiconductor wafers, which comprises rinsing with water, bringing the polished surfaces of the two semiconductor wafers into close contact with each other under clean conditions to directly join them, and then heating them. Each polished surface preferably has a surface roughness of 50.
nm or less.

[0006]

According to the present invention, impurities on the polishing surface can be removed by treating at least one of the polishing surfaces of the mirror-polished semiconductor wafer with a hydrofluoric acid-based solution. After that, the polishing surfaces are brought into close contact with each other. It is possible to make the joint stronger by directly joining it without the presence of foreign matter and then heating it.

[0007]

【Example】

(Example 1) 2 which was mirror-polished to have a surface roughness of 50 nm or less
Inch diameter n-type (100) silicon wafer (thickness 600
μm, specific resistance 1 Ω-cm), prepared in oxygen at 1100 ° C.
And a thermal oxide film of 600 nm was formed on the surface. With a diamond blade on the surface of this wafer,
Grooves having a depth of 100 μm and a width of 40 μm were formed on the grid at a pitch of 5 mm. Next, hydrofluoric acid, which is a hydrofluoric acid-based solution,
The ground layer was removed by treatment with a mixed solution of nitric acid-acetic acid. Then 4
It was immersed in a 0% ammonium fluoride solution to remove the oxide film layer, and then washed with water.

A 2-inch diameter n-type (100) silicon wafer (thickness 3
00 μm, specific resistance 60 Ω-cm) was prepared and washed with a sulfuric acid-hydrogen peroxide mixture solution.

The two wafers were further thoroughly washed in pure water, then freon-dried, and the dust floating amount was 20 / cm.
^In a clean room of ³ or less, both polishing surfaces (one of which has a groove) were directly contacted and pressed. As a result, a strong wafer bonded body was obtained.

After heating the joined body to 1200 ° C. in nitrogen, the joint surface was observed with an infrared microscope, and it was confirmed that the joints were joined without voids except for the groove portions. (Example 2) A p-type silicon wafer having a diameter of 2 inches and a specific resistance of 5 Ω-cm and an n-type silicon wafer having the same diameter and a specific resistance of 1 Ω-cm were prepared. Both of them have one surface mirror-polished with a surface roughness of 50 nm or less, and a thickness of 400 μm.
Is. Depth of 40μ at 3mm pitch on the polished surface of both wafers
A m-shaped and 100 μm-wide interdigital groove was formed by chemical etching. A photoresist is used as a mask for this etching, and the etching solution is hydrofluoric acid, which is a hydrofluoric acid-based solution.
A nitric acid-acetic acid mixture was used. These wafers were washed with water and dried, and then, in a clean room, the polished surfaces of both were brought into contact with each other so that the grooves were orthogonal to each other, and pressed to bond them.

After heating this wafer bonded body to 1100 ° C. in nitrogen, it was divided along a groove with a diamond blade to obtain a diamond pellet having a 3 mm opening. All diamond pellets showed sufficient rectifying characteristics.

[0012]

As described above, according to the present invention, it is possible to provide a semiconductor wafer bonding method capable of directly bonding semiconductor wafers to each other without interposing foreign matter.

Claims (2)

[Claims] 1. The surface of two semiconductor wafers is mirror-polished, and at least one of the polished surfaces is treated with a hydrofluoric acid-based solution and washed with water, so that the polished surfaces of the two semiconductor wafers are bonded to each other. A method for bonding semiconductor wafers, which comprises contacting the members directly under clean conditions to directly bond them, and then heating them. 2. The semiconductor wafer bonding method according to claim 1, wherein the mirror-polished surface has a surface roughness of 50 nm or less.