JPH03250666A - Manufacture of semiconductor film - Google Patents

Abstract

PURPOSE:To eliminate an etch-back process and manufacture an SOI substrate with throughput suitable for mass production by a method wherein after a singlecrystal silicone film epitaxially grown on a sapphire substrate is tightly adhered to an insulating surface of another substrate to be heated and joined, the sapphire substrate is removed from the singlecrystal silicon film. CONSTITUTION:A singlecrystal silicon film 2 is epitaxially grown on a sapphire substrate 1. On the other hand a silicon oxide film 4 is formed on the singlecrystal silicon substrate 3 by means of thermal oxidation. Then both substrates are adhered to each other so that the singlecrystal silicon film 2 and the silicon oxide film 4 come into contact with each other. The assembly is put into a heating furnace in this state to be subjected to predetermined heat treatment. Then the sapphire substrate 1 is removed from the silicon sub strate 3. Since adhesive force between the silicon oxide film 4 and the singlecrystal silicon film 2 is stronger than adhesive force between the sapphire substrate 1 and the singlecrystal silicon film 2 at this time, only the sapphire substrate 1 is removed resulting in an SOI structure where the singlecrystal silicon film 2 remains on the silicon oxide film 4 on the silicon substrate 3.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to a so-called 5OI (Silicon
The present invention relates to a method of manufacturing a single crystal silicon film called an on-in-layer structure.

The single crystal silicon film produced by the method of the present invention can be used in active matrix liquid crystal display devices, highly integrated L
It can be used in many fields such as SI, high-voltage devices, radiation-resistant devices, and three-dimensional integrated circuits.

(Prior art) There are several methods for SOI structure formation technology, and a general explanation is given in detail in "S○■ Structure formation technology" (published by Sangyo Tosho Co., Ltd., 1988). One of these is silicon wafer direct bonding technology.

In silicon wafer direct bonding technology, single crystal silicon substrates with oxide films formed on one surface are brought into close contact with each other so that the oxide films are in contact with each other, and heat treatment is performed at approximately 700°C in an oxidizing atmosphere to bond the oxide films directly to each other. to join. Thereafter, one silicon substrate is etched using an etch-back method until a predetermined film thickness is achieved, thereby forming an SOI substrate.

(Problems to be Solved by the Invention) In the silicon wafer direct bonding technology described above, it is necessary to etch back one silicon substrate to a thickness that provides the desired device characteristics, but the following problems occur during this process. Sign.

(1) When etching back using the dry etching method, the etch rate of silicon is
If E is normally about 8000 A/min and the thickness of the silicon substrate needs to be about 500 μm from the viewpoint of its strength, the time required for etchback will be several hours to more than ten hours, resulting in extremely low throughput.

(2) When etching back using the dry etching method, damage is caused to the silicon substrate that will later become the element forming surface. Extra processing steps such as wet surface treatment and sacrificial oxidation are required later to remove the damage.

(3) When etching back by wet etching, the uniformity of etching is poor, which becomes a serious problem as the diameter becomes larger.

(4) When etching back using a wet etching method, it is necessary to mask the exposed surface and side surfaces of one of the silicon substrates serving as a support substrate, which requires an extra step.

The present invention eliminates the etch-back process found in conventional methods, has a throughput suitable for mass production, has in-plane uniformity that can accommodate larger diameters, and uses a process that does not damage the element formation surface. The purpose is to manufacture.

(Means for Solving the Problems) In the present invention, a first substrate is formed by epitaxially growing a single crystal silicon film on a sapphire substrate.

and a second substrate whose surface is an insulator.

After the two plates are brought into close contact so that the single crystal silicon film of the first substrate and the insulating surface of the second substrate are in contact with each other, and the single crystal silicon film and the insulating surface of the second substrate are bonded by heating. , pull the sapphire substrate apart.

At least the second substrate has an insulating surface.

A thermal oxide film formed on the surface of a single crystal silicon substrate,
Furthermore, there are those in which a silicon nitride film is formed thereon, and those in which a silicon oxide film or a silicon nitride film is formed on the surface of a glass substrate. In the case of a second substrate in which an insulating film is formed on a silicon substrate, the silicon substrate may not have a semiconductor element formed thereon, or may already have a semiconductor element formed thereon.

(Example) One embodiment will be explained with reference to FIG.

(A) Thousands of single crystal silicon films 2 are formed on a sapphire substrate 1 by a well-known method such as thermal decomposition of SiH4.
Epitaxially grown to human thickness.

On the other hand, a silicon oxide film 4 is formed to a thickness of about 10,000 to 15,000 wafers on a single crystal silicon substrate 3 by a thermal oxidation method.

(B) Both substrates are pasted together so that the single crystal silicon film 2 and the silicon oxide film 4 are in contact with each other. In this state, it is placed in a heating furnace and subjected to heat treatment at 900 to 1000°C for 30 to 60 minutes.

(C) Separating the sapphire substrate 1 from the silicon substrate 3. At this time, since the adhesion between the silicon oxide film 4 and the single crystal silicon film 2 is stronger than the adhesion between the sapphire substrate 1 and the single crystal silicon film 2, only the sapphire substrate 1 is separated. .

An SOI structure is obtained in which the single crystal silicon film 2 remains on the silicon oxide film 4 on the silicon substrate 3.

FIG. 2 represents another embodiment.

For example, a silicon oxide film 5 is formed as a mask material on the sapphire substrate, and the silicon oxide film 5 is patterned by photolithography and etching so that the sapphire substrate 1, which will later become an active region in the SOI substrate, is exposed.

A single crystal silicon film 2 is epitaxially grown on the exposed sapphire substrate. The single crystal silicon film 2 is made to have the same thickness as the silicon oxide film 5, or when it is formed thinner than the silicon oxide film 5 as will be explained later in FIG. 3, the silicon oxide film 5 is etched so that the single crystal silicon film 2 protrudes. let The thickness of the single-crystal silicon film 2 is determined to be an appropriate value in consideration of the subsequent sapphire substrate peeling process and the depth of the active region thereafter. The thickness of the single crystal silicon film 2 is, for example, about 3000.

On the other hand, a silicon oxide film 4 is formed on the silicon substrate 3 in the same manner as in FIG.

Both substrates are pasted together so that the single crystal silicon film 2 and the silicon oxide film 4 are in contact with each other, and in this state they are placed in a heating furnace for 90 minutes.
Heat treatment is performed at 0 to 1000°C for 30 to 60 minutes.

When the sapphire substrate 1 is separated from the silicon substrate 3, an SOI structure is formed in which the single crystal silicon film 2 partially remains on the silicon oxide film 4 on the silicon substrate 3. In this SOI structure, the single-crystal silicon film 2 is patterned, and an S◯◯◯ substrate is formed with element isolation in the active region. Therefore, the element isolation step can be omitted.

When selectively growing the single crystal silicon film 2 on the sapphire substrate 2, the thickness of the single crystal silicon film 2 is formed to be thinner than the thickness of the silicon oxide film 5, as shown in FIG. 3(A). , If the silicon oxide film 5 is etched so that the single crystal silicon film 2 is etched as shown in (B), the single crystal silicon film 2 comes into close contact with the silicon oxide film 4,
Moreover, the dimensional accuracy in the lateral direction is also improved. When the state shown in FIG. 3(B) is created, a cavity is formed between the silicon oxide film 5 and the second substrate surface, and the gas sealed therein may expand. Both substrates may be brought into close contact with each other inside.

As a heat treatment for bonding between the single crystal silicon film 2 and the silicon oxide film 4, instead of putting it in a heating furnace,
Other heating means may be used, such as scanning by irradiating a laser beam from the sapphire substrate 1 side or scanning by irradiating a hot ray from the sapphire substrate 1 side or the silicon substrate 3 side.

(Effects of the Invention) In the present invention, the single crystal silicon film epitaxially grown on the sapphire substrate is brought into close contact with the insulating surface of the second substrate, and after being heated and bonded, the sapphire substrate is separated from the single crystal silicon film. Since we obtain the SOI structure,
There is no need for an etch-back process, and the S○I structure can be easily realized with high throughput.

The single-crystal silicon film on which the device is formed is formed by epitaxial growth, and there is no etch-back process, so the film has excellent in-plane uniformity and is easy to achieve the desired film thickness. Further, there is no damage to the element forming surface.

Sapphire substrates are more expensive than silicon substrates. However, if a ready-to-crystal silicon film formed on a sapphire substrate is closely attached to, for example, a silicon oxide film formed on a silicon substrate and heated to bond the single crystal silicon film and silicon oxide film, the sapphire substrate After cleaning the sapphire substrate surface, the single crystal silicon film on it will be gone.

By performing epitaxial growth again, the single crystal silicon film can be regenerated and used.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a process showing one embodiment, Fig. 2 is a cross-sectional view of an intermediate process showing another embodiment, and Fig. 3 is a method of selectively forming a single crystal silicon film on a sapphire substrate. It is a process sectional view. ■...Sapphire substrate, 2...Single crystal silicon film, 3...Silicon substrate, 4...
...Silicon oxide film.

Claims (1)

[Claims] (1) A first substrate in which a single crystal silicon film is epitaxially grown on a sapphire substrate and a second substrate whose surface is an insulator, A method for manufacturing a semiconductor film, in which both substrates are brought into close contact with each other so that their insulating surfaces are in contact with each other, the single crystal silicon film and the insulating surface of a second substrate are bonded by heating, and then the sapphire substrate is separated.