JPH027414A - Formation of soi thin film - Google Patents

Abstract

PURPOSE:To form an SOI thin film in a uniform thickness by a method wherein an insulating film having regularly protruding and recessed parts on an extremely thin film is formed, a semiconductor film having a film thickness capable of sufficiently absorbing a laser beam is formed on it, this film is then irradiated with the laser beam and heated, the extremely thin film is heated, melted and recrystallized and, after that, all upper-layer films are removed. CONSTITUTION:A silicon oxide film 2 and a polysilicon oxide film 3 are formed one after another on a silicon substrate 1. A silicon oxide film is formed on them; a stripe pattern is processed; after that, a silicon oxide film is formed on it; a silicon oxide film 4 having protruding and recessed parts is formed. Lastly, a polysilicon film 5 is formed. The surface of a substrate where these films have been constituted is irradiated with an argon gas laser; when this laser is scanned, the polysilicon film 5 is heated, melted and recrystallized by the laser. The heat accumulated in the polysilicon film 5 is conducted to the polysilicon thin film 3; this film is heated, melted and recrystallized. After that, the silicon film 5 and the silicon oxide film 4 are removed; an SOI substrate having a single-crystal silicon thin film with a film thickness of about 0.1mum or lower is formed on the silicon oxide film 2.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to 5ol (semiconductor on insulator).
tor) A method for forming a thin film of single crystal semiconductor on an insulating layer by laser beam annealing a substrate.

(Prior art) Conventionally, in order to form a single crystal semiconductor film having an SO structure on an insulating layer, a polycrystalline or amorphous semiconductor film formed on an insulating layer is heated and melted using a laser. The method used was to crystallize it into a single crystal. However, if the target single crystal semiconductor film is extremely thin, for example, the film thickness is 0.1
In the case of about .mu.m, it is difficult to sufficiently absorb laser light due to the thinness of the polycrystalline or amorphous semiconductor thin film, and therefore it is difficult to melt φ recrystallization and single crystallization.

Therefore, when forming a single crystal semiconductor thin film with a thickness of about 0.1 μm on an insulating layer, the following method has been used. First, as shown in FIG. 2(a), a silicon substrate 1 is used as a semiconductor substrate, a silicon oxide film 2 with a thickness of 1 μm is used as an insulating film, and
A polycrystalline silicon film 3 having a thickness of 0.5 μm is sequentially formed as a semiconductor film. At this time, the film thickness of the semiconductor is sufficient to absorb the argon gas laser light. By subjecting this substrate to laser beam annealing, the polycrystalline silicon film 3 was heated, melted, and recrystallized. After that, Figure 2
As shown in (b), the polycrystalline silicon film 3 has a thickness of 0.1 μm.
The polycrystalline silicon film 3 was processed into an extremely thin film by polishing or etching until the thickness was less than m.

(Kusuno et al., Proceedings of the 35th Applied Physics Conference, Part 2, page 613, 29a-M-4) (Problem to be solved by the invention) However, the silicon film recrystallized by laser annealing It is difficult to accurately thin the film to a set thickness of about 0.1 μm by polishing or etching. In other words, polishing proceeds in a plane parallel to the lower bottom surface of the silicon substrate 1, so if the upper and lower bottom surfaces of the silicon substrate 1 used are not completely parallel, the entire surface of the substrate will be uniformly coated with an extremely thin film. It's difficult to do. Furthermore, complete uniformity within the substrate is required for the polishing rate and etching rate, but the polishing rate of existing polishing methods is not sufficient to form a thin film of 0.1 μm or less.

The object of the present invention is to
An object of the present invention is to provide a method for forming an OI thin film with a uniform thickness.

(Means for Solving the Problems) The present invention involves forming an extremely thin film made of a polycrystalline or amorphous semiconductor on a substrate having an insulating layer on at least the surface, and then forming an insulating film having regular irregularities thereon. form a film,
After forming a polycrystalline or amorphous semiconductor film having a thickness sufficient to absorb laser light thereon, laser light is irradiated to sufficiently heat the polycrystalline or amorphous semiconductor film. Heat conduction from the crystalline or amorphous semiconductor film heats and melts the ultra-thin polycrystalline or amorphous thin film to recrystallize it, and then removes all films above the ultra-thin semiconductor film. SO characterized by
This is a thin film forming method.

(Example) Hereinafter, the present invention will be explained using Examples. In this example, a polycrystalline silicon film is used as a semiconductor film, a silicon oxide film is used as an insulating film, and a silicon substrate with a silicon oxide film formed on its surface is used as a substrate having an insulating layer on its surface.
An argon gas laser is used as the laser.

FIG. 1(a) is a cross-sectional view of a sample subjected to laser annealing. First, as shown in FIG. 1(a), a silicon substrate 1
CVD silicon oxide film 2 and polysilicon oxide film 3 on top.
Film thickness: 1.0 μta 10.1 tt by method D
Formed sequentially with m. A silicon oxide film with a thickness of 0.1 μm is formed on this, and this film is processed into a stripe pattern with a width of 10 μm and a pitch of 15 μm.
A 1 μm silicon oxide film is formed with a pitch of 15 μm.
．． Four silicon oxide films with 1 μm unevenness are created.

Finally, a polysilicon film 5 having a thickness of 0.5 μ is formed.

When the surface of the substrate having the above film structure is irradiated and scanned with an argon gas laser having a laser power of 12 watts at a speed of 5 mm/see, the polysilicon film 5 is heated by the laser, melted, and recrystallized. The heat accumulated in the polysilicon film 5 is conducted to the polysilicon thin film 3 using the silicon oxide film 4 as a medium, and heats, melts, and recrystallizes the polysilicon thin film 3. At this time, heat is conducted more easily in the thinner part of the silicon oxide film 4 than in the thicker part, so in the polysilicon thin film 3, the temperature is higher under the thinner part of the silicon oxide film 4, and the temperature in the thicker part of the silicon oxide film 4 is higher. The temperature is lower at the bottom. As a result, in the polysilicon thin film 3, recrystallization proceeds from the lower temperature portion, and a single crystal silicon thin film is formed under the thicker portion of the silicon oxide film 4.

After recrystallizing polysilicon thin film 3, silicon film 5 and silicon oxide film 4 are removed by etching, and an SOI substrate having a single crystal silicon thin film with a thickness of 0.1 μm on silicon oxide film 2 is created.

In this example, a polycrystalline silicon film was used as the semiconductor film, a silicon oxide film was used as the insulating film, a silicon substrate with a silicon oxide film on the surface was used as the substrate having an insulating layer on the surface, and an argon gas slave was used as the laser. Other types of polycrystalline semiconductor films or amorphous semiconductor films, other types of semiconductor oxide films or nitride films, other types of substrates having insulating layers on their surfaces, and other types of lasers may be used.

(Effects of the Invention) As described above, according to the present invention, a single crystal thin film having a thickness of about 0.1 μm or less can be formed uniformly and accurately on an insulating layer.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a sample in an embodiment of the present invention, and FIG. 2 is a sectional view of a sample in a conventional example. The numbers in the figure indicate the following. 1, silicon substrate, 2.4, silicon oxide film, 3,
is a polysilicon film.

Claims (1)

[Claims] After forming an extremely thin film made of polycrystalline or amorphous semiconductor on a substrate that has an insulating layer on at least the surface, an insulating film with regular irregularities is formed on top of it, and a laser beam is sufficiently applied on top of the insulating film. After forming a polycrystalline or amorphous semiconductor film having a thickness that allows absorption, laser light is irradiated to sufficiently heat the polycrystalline or amorphous semiconductor film, and the polycrystalline or amorphous semiconductor film is removed. SOI characterized in that, after heating and melting the ultra-thin thin film made of polycrystalline or amorphous semiconductor to recrystallize it by heat conduction, all films above the ultra-thin semiconductor thin film are removed. Thin film formation method.