JPS6130024A - Formation of soi - Google Patents

Abstract

PURPOSE:To obtain SOI by stacking a film A which is not liquified at the melting point of Si, a film B which is more easily vaporized than the film A on a Si thin film and then stacking a film C which is more difficult to be vaporized than the film B to a part of said film B and then single-crystal-lizing a thin film around the region not covered with the film C with the heating during a short period of time. CONSTITUTION:A thin film 6 of poly-Si, a thin film 7 of SiO2A, a thin film 8 of poly-SiB and a thin film 9 of SiO2C are stacked on a quartz substrate 5. It is irradiated with laser beam during a short period of time, Si 6 is melted and heating is suspended. Heat of film 6 is not dispersed to the substrate 5, convection is not generated at the surface of substrate due to the heating within a short period of time, Si is vaporized from an aperture 10 getting the vaporization heat, cooling is effective and the aperture is cooled quicker than the other region. Thereby, the Si single crystal region can be obtained around the aperture 10. In the case of laser beam heating, use of SiO2 film in the thickness of about 850Angstrom is effective. According to this structure, the SOI single crystal can be formed at the desired region regardless of the underlayer structure.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention involves heating a semiconductor thin film on an insulating layer to melt it in a bath;
It relates to a method of solidifying and forming a single crystal.

(Prior art and its problems) Conventionally, a polycrystalline or amorphous semiconductor thin film on an insulating film is heated, melted, and solidified to produce single crystals or crystals with large grain sizes close to single crystals (SOI: 8emic).
Various studies have been conducted on methods to obtain an inductor (on inductor).In general, a part of the substrate is heated and melted in a short time using an electron beam, laser beam, flash lamp, strip heater, etc. There are various methods for cooling and solidifying the material by conducting heat into the substrate or by radiating heat from emitted light.

One is a method (seeding epitaxial growth method) in which the semiconductor film is provided at a location (seed) in contact with a single crystal substrate, and a single crystal continuous with the substrate is grown by solidifying from this seed.

In addition, the shape of the heating beam has been carefully modified so that the rear part of the interface between the heated and molten part and the solid part (solid-liquid interface) is convex in the direction of the beam, so that the microcrystals generated during the initial beam scan can be removed. A method to obtain large single crystals by propagating grains so that their crystallinity is constantly expanded (shaped beam method)
There is.

This is a method of extending the properties of the crystal grains generated at the beginning of forging during solidification to a desired location by modifying the shape of the lower part of the semiconductor thin film mentioned above to control the path of heat escape to the substrate. (heat sink method).

Shikashi, SeegainingEbitaxial method requires an extra area called a seed, and when making a transistor for LSI, a certain distance between the necessary gate part of the single crystal and the seed is required to make a large single crystal. In reality, it is difficult to make a high-quality single crystal for the gate part.

With the shaped beam method, there is no continuity between the single crystals between different beam paths, grain boundaries are always present, and the single crystal region can only be formed in the form of a stripe of beam travel, so it is possible to create a transistor anywhere. This is inconvenient for application to such LSIs.

Although the heat sink method has the advantage that it does not require extra area and can create a single crystal in any location by providing a heat sink part on the base, it has the disadvantage that it depends on the base structure, and it is difficult to make devices in multiple layers. In such cases, there are limitations on where the single crystal can be made, or it is necessary to provide a buffer layer between layers, making the manufacturing process complicated.

FIG. 1 is a sample oil surface diagram for SOI formation using the conventional heat sink method. An electrically insulating 8i02 film 2 is attached to a silicon substrate 1 with high thermal conductivity, a part of which is thinned to provide a heat sink 4 that allows heat to easily escape, and a polycrystalline or amorphous film is placed on top of the heat sink 4. A high quality silicon thin film 3 is grown. When the heat sink 4 and the silicon thin film 3 around it are heated and melted by a light beam, etc., and then the heating a is removed, a lot of heat escapes from the heat sink 4 to the substrate 1, so that the silicon thin film 3 directly above the center of the heat sink 4 is heated and melted. It begins to solidify, and as the surrounding area cools and solidifies, epitaxial growth occurs using the first solidified crystal grains as nuclei, so that at least a single crystal larger than the heat sink 4 is grown.

As mentioned earlier, this method has the advantage of being able to form a single crystal in a predetermined location, such as the heat sink part 4, but the heat sink must be able to easily dissipate heat. If a device is fabricated on the base, heat conduction will be poor, making it impossible to selectively form a heat sink and a single crystal will not grow.

(Objective of the Invention) An object of the present invention is to provide a method for eliminating the above-mentioned drawbacks and forming a single crystal semiconductor film at any location regardless of the underlying structure.

(Structure of the Invention) The present invention provides an SOI forming method in which a semiconductor thin film on an insulating layer is heated, melted, and solidified to make the semiconductor thin film into a single crystal. A film that does not liquefy (hereinafter referred to as the cap film) is provided, and a film made of a substance that evaporates more easily than the cap group (hereinafter referred to as the evaporation film) is provided on top of the film, and a part of the film made of a substance that is more difficult to evaporate than the evaporation film is placed on top of the evaporation film. It is constructed by covering the semiconductor thin film, and then subjecting it to a short-time heat treatment to form a single crystal of the semiconductor thin film, centering on the portions not covered by the film that is difficult to evaporate.

(Example) The present invention will be described below based on an example and with reference to the drawings. In the explanation, silicon, which is commonly used as a semiconductor, will be used as an example.

FIG. 2 shows a cross-sectional structure of a sample according to the present invention.

Here, 5 is a quartz substrate, which has poor heat conduction, and regardless of the underlying structure, it is better to have poor heat dissipation.

For example, it may be a semiconductor substrate with a P film formed on its surface. 6
is a polycrystalline silicon film to be made into a single crystal, and its thickness is 0.
It is about 5 μm. A cap film 7 prevents contamination and deformation of the silicon film 6 during heating and is made of SiO2 or Si3N4, which does not liquefy even at the melting point of silicon. The thickness is 8
i0. If so, 0.5 μm is sufficient. Reference numeral 8 denotes a polycrystalline silicon film (evaporation film), which is a material that evaporates more easily than the cap film, and has a thickness of about 0.1 μm. 9 is an S I 02 film for completely preventing evaporation of the evaporation film 8, and its thickness is approximately 05 μm.
It is m.

This structure is heated using a laser beam, electron beam, or lamp annealing to melt the silicon film 6 and then stop heating. The annealing conditions are, for example, an output of 5 W and a beam diameter of 40 μm in the case of Arm/-.

The heat from the silicon film 6 escapes in one direction in the lateral direction through the silicon film 6, and in the other by radiation. However, the heat cannot escape to the quartz substrate 5 due to poor heat conduction of quartz.

Furthermore, since the outside is a gas such as air or a vacuum, thermal conductivity is low, and since heating is very short, convection does not occur, and generally heat does not escape from the surface of the sample. but,
Since the recon evaporates from the aperture f1510, there is a lot of heat of vaporization.This method is based on heating by the beam 17, and the evaporation prevention film 9 is an antireflection film, for example, an 8i (J, film with a thickness of 850X). (Increase the surrounding temperature,
Cooling can be further efficiently performed through the opening 10.

In the explanation, silicon is used as the semiconductor film 6 and 8i0. or S i , N4. Although the description has been made using silicon as the evaporative substance 8, it is clear that any material may be used as long as it satisfies the relationship of ease of evaporation near the melting point of the semiconductor film 6.

(Effects of the Invention) According to the method of the present invention, an SOI single crystal can be formed at any location regardless of the underlying structure.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a sample for forming 80I using the conventional heat sink method, where 1 is a silicon substrate, 2Fi, 8i0-
The film 3 is a polycrystalline silicon film and is a 4σ heat sink. FIG. 2 is a cross-sectional view of a sample for forming 80I according to the present invention, in which 5 is a quartz substrate, 6 is polycrystalline silicon, 7 is a cap film such as Sin, and 8 is a film that evaporates more easily than cap film 7. 9 is an evaporation prevention film S10. Or 8i, N, , 1O are openings. Engineering S Technology Academy Aryu 1 diagram

Claims (1)

[Claims] In an SOI forming method in which a semiconductor thin film of an insulating layer is heated, melted, and solidified to single-crystallize the semiconductor thin film, a film (hereinafter referred to as a cap film) that does not liquefy even at the melting point of the semiconductor is provided on the surface of the semiconductor thin film. A film made of a substance that evaporates more easily than the cap film (hereinafter referred to as evaporation film) is provided on top of the cap film, and a part of the top of the evaporation film is covered with a film that evaporates more easily than the evaporation film, and then heat treatment is performed for a short time. A method for forming an SOI, characterized in that the semiconductor thin film is single-crystalized mainly in the portions not covered by the film that is difficult to evaporate.