JPH061752B2 - Method for joining semiconductor wafers - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for bonding semiconductor wafers such as silicon.

[Technical background of the invention and its problems]

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, 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, and the like.
However, the deposition rate is slow in various conventional vapor deposition methods,
For example, there is a problem that it takes an extremely long time to form a semiconductor layer having a thickness of several 100 μm. Further, the method of joining the semiconductor wafers with the adhesive layer made of different materials has a disadvantage that the adhesive layer material is diffused into the semiconductor when heated, or a compound is generated to cause alteration. These problems can be solved if the semiconductor wafers can be directly bonded to each other without the presence of foreign matter.

The present inventors have found that after the mirror-polished semiconductor wafers are subjected to hydrophilic treatment on the polished surfaces, and then pressure-bonded in a clean atmosphere, the semiconductor wafers are bonded to each other extremely strongly, and this is first proposed. Yes (Japanese Patent Publication No. Sho 62-27)
040 publication). According to this method, a bonded body of semiconductor wafers can be obtained with virtually no intervening foreign matter.

However, it has been found that when this method is used for bonding semiconductor wafers having a large diameter of several inches, it is very difficult to adhere the entire surface due to the influence of the warp of the wafer. The main reason for this is that residual gas is left behind on a part of the adhesive surface.

[Object of the Invention]

An object of the present invention is to provide a semiconductor wafer bonding method capable of easily and firmly bonding large-area semiconductor wafers.

[Outline of Invention]

According to the present invention, the surfaces of two semiconductor wafers are mirror-polished, and at least one end is opened at the peripheral edge of the semiconductor wafer on the polished surface of at least one of the semiconductor wafers so that a gas can be prevented from being trapped in the bonding surface. A semiconductor wafer bonding method is characterized in that a groove having a function is provided, and the respective polishing surfaces of these two semiconductor wafers are brought into close contact with each other under clean conditions to directly bond them. The surface roughness of each polished surface is preferably 500 Å or less. Further, it is preferable to perform a hydrophilic treatment such as washing with water, that is, a treatment for making the surface condition more hydrophilic, before these polishing surfaces are bonded.

Thus, by providing a groove on the surface of the semiconductor wafer to be bonded, a gas such as air is not trapped in the surface at the time of bonding and the bonding is not hindered, and the entire surface of the semiconductor wafer having a large diameter can be bonded reliably. be able to. The shape, number, direction, etc. of the formed grooves should be selected as needed.
If the semiconductor wafer has a relatively small diameter, for example, cross-shaped grooves intersecting at the center of the plane may be used. In the case of applying to a large-diameter wafer for obtaining a large number of pellets, one method is to form a groove in accordance with a future scribe line. If the pitch of the groove is made fine, the adhesion becomes easy, but the substantial adhesion area is naturally small. A diamond blade, chemical etching, or the like is used to form the groove. The depth of the groove is not particularly limited, but if it is too deep in relation to the thickness of the wafer, it is easily broken. In short, this groove has only to have a function as a ventilation passage so that gas is not trapped on the bonding surface, and at least one end thereof may be opened to the outside at the wafer peripheral edge. This is because if the gas is confined within the bonding surface, even if the gas is temporarily strongly bonded, it will be easily peeled off due to the gas expansion inside due to the temperature rise.

〔The invention's effect〕

According to the present invention, semiconductor wafers having a large area can be firmly bonded to each other substantially without any foreign matter. The obtained semiconductor bonded body can be heated to, for example, the heat resistant temperature of the semiconductor itself because no foreign matter is present, and can be widely applied to the manufacture of various semiconductor devices.

Example of Invention

(1) Prepare a 2-inch diameter n-type (100) silicon wafer (thickness 600 μm, specific resistance 1 Ω-cm) mirror-polished to a surface roughness of 500 Å or less, and treat it in oxygen at 1100 ° C. for 30 minutes, A 6000Å thermal oxide film was formed on the surface. With a diamond blade, a depth of 100
Grooves having a width of 40 .mu.m and a width of 40 .mu.m were formed in a grid pattern with a pitch of 5 mm. Then, the crushed layer was removed by treating with a mixed solution of hydrofluoric acid-nitric acid-acetic acid. Next, it was immersed in a 40% ammonium fluoride solution to remove the oxide film layer, boiled in aqua regia and washed with water (hydrophilization treatment).

Separately, a 2-inch diameter n-type (100) silicon wafer (thickness 300 μm, specific resistance 60 Ω-cm) mirror-polished to a surface roughness of 500 Å or less was prepared and washed with a sulfuric acid-hydrogen peroxide mixture solution.

These two wafers are further thoroughly washed in pure water, then freon dried, and both polished surfaces (one is grooved) in a clean room with a dust floating amount of 20 / cm ³ or less.
Was directly contacted and pressed. As a result, a strong wafer bonded body was obtained.

The bonded body was heated to 1200 ° C. in nitrogen, but no change was observed. Further, as a result of observing the joint surface with an infrared microscope, it was confirmed that the joints were bonded without voids except the groove.

(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 to have a surface roughness of 500 Å or less, and have a thickness of 400 μm. Polished surface of both wafers with 3mm pitch, depth 40μm, width 100μ
The m-shaped interdigital groove was formed by chemical etching. A photoresist was used as a mask for this etching, and a mixed solution of hydrofluoric acid-nitric acid-acetic acid was used as an etching solution. These wafers were boiled in nitric acid, washed with water, dried, and brought into contact with each other in such a manner that their polished surfaces were perpendicular to each other in a clean room, and pressed and bonded.

After heating the obtained wafer bonded body to 1100 ° C. in nitrogen, divide along the groove with a diamond blade to obtain 3 mm
It was a mouth diode pellet. All diode pellets showed sufficient rectification characteristics.

Continuation of the front page (56) References JP-A-56-13773 (JP, A) JP-B 37-114 (JP, B1) JP-B 49-26455 (JP, B1)

Claims (3)

[Claims] 1. The surface of two semiconductor wafers is mirror-polished,
At least one end of the polishing surface of at least one semiconductor wafer is opened at the periphery of the semiconductor wafer, and a groove having a function as a ventilation path is provided on the bonding surface so that gas is not trapped. A method for joining semiconductor wafers, wherein the respective polished surfaces are brought into close contact with each other under clean conditions to be directly joined. 2. The method for bonding semiconductor wafers according to claim 1, wherein the mirror-polished surface has a surface roughness of 500 A or less. 3. The method for joining semiconductor wafers according to claim 1, wherein each polishing surface is subjected to a hydrophilic treatment before the two semiconductor wafers are brought into close contact with each other.