JPH03145716A - Manufacture of semiconductor thin film - Google Patents

Abstract

PURPOSE:To obtain a single crystal semiconductor thin film of good quality having no cracks and the like by a method wherein an amorphous or polycrystalline silicon film is formed in narrow-strip shape on an insulated substrate, and said polycrystalline film is brought into the state of single crystal by scanning a laser beam in the direction intersecting with the polycrystalline silicon film. CONSTITUTION:A base layer 2 such as a silicon oxide film, a silicon carbide film, an aluminum oxide film and the like, for example, is formed on an insulated substrate 1 consisting of a quartz substrate and the like, an amorphous or polycrystalline silicon film 3 are formed thereon in band-like shape, and besides, a protective film 4 consisting of silicon oxide, silicon carbide or aluminum oxide and the like is formed thereon. Then, the amorphous or polycrystalline silicon film 3 is single-crystallized by scanningly projecting a laser beam in the direction intersecting with the band-like amorphous or polycrystalline silicon film 3 from the side of the protective film 4 or from the side of the insulated substrate. According to this method, the scanning length of the laser beam on the amorphous or polycrystalline silicon film can be made short, the condition of crystallization can be stabilized, and as a result, a single crystal of good quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a semiconductor thin film, and more particularly to a method for manufacturing a semiconductor thin film in which a silicon film is irradiated with a laser beam to monocrystallize the semiconductor thin film.

(Prior Art and Problems) Conventionally, there is a laser beam crystallization method in which polycrystalline or amorphous silicon is irradiated with a laser beam to form a single crystal. In this laser beam crystallization method, various attempts have been made to obtain a high-quality single-crystalline film free from cracks from a polycrystalline or amorphous silicon film.

That is, in the laser beam crystallization method, when molten silicon is solidified by laser irradiation, the difference in thermal expansion coefficient between the insulating substrate and the silicon film during cooling from the melting point to room temperature causes distortion. Since the thickness of the silicon film is extremely thin compared to the insulating substrate, expansion and contraction in the plane direction is determined by the substrate, and tensile strain occurs in the silicon film. Attempts are made to alleviate this tensile strain by interposing, for example, a silicon oxide film between the insulating substrate and the silicon film, but the relaxation is not completely resolved and microcracks occur in the silicon film due to the relaxation being done by the silicon film itself. That's what happens.

In order to alleviate such tensile strain during single crystallization, Japanese Patent Laid-Open No. 51-210638 discloses that after forming an amorphous or polycrystalline silicon film on an insulator, It has been proposed to separate a polycrystalline silicon film into islands using ordinary photolithography technology to reduce the area of the film to be single-crystallized, thereby achieving complete single-crystallization in small-area units.

However, in this conventional method for manufacturing semiconductor thin films, the laser beam must be precisely positioned and irradiated onto regions of the amorphous or polycrystalline silicon film separated into islands, which requires extremely advanced manufacturing. Technology will be required.

(Purpose of the Invention) The present invention was devised in view of the problems of the prior art, and provides a semiconductor thin film single crystal of high quality that does not cause cracks or the like to occur in the semiconductor thin film irradiated with a laser beam. The object of the present invention is to provide a method for manufacturing a semiconductor thin film that can be obtained.

(Means for solving the problem) According to the present invention, a laser beam is irradiated onto an amorphous or polycrystalline silicon film formed on an insulating substrate to melt and solidify the amorphous or polycrystalline silicon film. In the method of manufacturing a semiconductor thin film which is made into a single crystal by forming a band-shaped amorphous or polycrystalline silicon film on the insulating substrate, the amorphous or polycrystalline silicon film is There is provided a method for manufacturing a semiconductor thin film characterized by single crystallization by scanning a laser beam, thereby achieving the above object.

(Example) Hereinafter, the present invention will be explained in detail based on the accompanying drawings.

FIG. 1 is a cross-sectional view for explaining the film structure of a semiconductor thin film used in the method of manufacturing a semiconductor thin film according to the present invention.
2 is an insulating substrate, 2 is a base layer, 3 is an amorphous or polycrystalline silicon film, and 4 is a protective film.

The insulating substrate 1 is made of #7059 glass, a quartz substrate, or the like.

A base layer 2 is formed on the insulating substrate 1. This base layer 2 is provided to prevent a film to be single-crystallized, which will be described later, from being contaminated by the insulating substrate 1 and to alleviate thermal shock when irradiated with a laser beam. As such a base layer 2, for example, silicon oxide (SiO2), silicon carbide (SiC), aluminum oxide (AI203) film, etc. are suitably used. When forming the base layer 2 with a silicon oxide film, for example, a thickness of 0.05 to 2
If it is formed with a silicon carbide film, it is formed with a thickness of about 0.05 to 2 μm using a plasma CVD method, for example.
In the case of forming an aluminum oxide film, it is formed to a thickness of about 1 μm by sputtering, for example.

On the base layer 2, an amorphous or polycrystalline silicon film 3 is formed.
form. This amorphous or polycrystalline silicon film 3 is formed into a plurality of strips.

This silicon film 3 is formed to have a width of, for example, about 5 to 1000 μm.

When this silicon film 3 is formed of an amorphous silicon film, it is formed to a thickness of about 0.05 to 2 μm using a plasma CVD method, and when it is formed using a polycrystalline silicon film, it is formed using an LPCVD method.
It is formed to a thickness of about 0.05 to 2 μm using a method. This amorphous silicon film or polycrystalline silicon film is formed on the entire surface of the base layer 2, a photoresist is applied to form a mask, and the film is immersed in a 1 to 10% fluoro-nitric acid solution (HNO3+HF) for several seconds to several minutes. It is formed into a band shape by immersing it for a certain amount of time and etching away a predetermined portion.

Next, heat at a temperature of 500 to 600°C for about 2 hours,
Hydrogen in the amorphous or polycrystalline silicon film is discharged.

Next, silicon oxide (S]02)-silicon carbide (SiC) is deposited on the amorphous or polycrystalline silicon film 3.
Alternatively, a protective film 4 made of aluminum oxide (A I 203 ) or the like is formed.

Next, as shown in FIG. 2, a laser beam is scanned and irradiated from the protective film 4 side or from the insulating substrate 1 side in a direction intersecting the band-shaped amorphous or polycrystalline silicon film 3. By doing so, the amorphous or polycrystalline silicon film 3 is made into a single crystal. Note that the scanning direction of the laser is not limited to the direction perpendicular to the band-shaped amorphous or polycrystalline silicon, but may also be scanned so as to intersect at a predetermined angle. 100μm
A continuous wave argon laser with a power of 0 and a power of 5 to 20 W is preferably used, and the scanning speed is about 1 to 20 cm/sec. Furthermore, a laser beam having a so-called bimodal intensity distribution is preferably used.

As shown in Fig. 3, the beam intensity on both sides of the laser beam in the scanning direction is made stronger than the central part, so that the laser beam intensity on both sides of the laser beam in the scanning direction of the amorphous or polycrystalline silicon film is increased. For example, one laser beam may be split with a Fresnel lens to form a so-called bimodal beam shape, and then passed through an aperture to scan the base portions on both sides of the bimodal beam. By cutting, both ends of the beam are made steeper,
Finally, an ND filter is applied to the center of the beam to make the beam intensity on both sides stronger than the center so that both sides can be fused. When such a laser beam is scanned so as to intersect with the band-shaped amorphous or polycrystalline silicon film 3, an island-shaped single crystal region can be formed at the same time as the laser beam is scanned. In addition, after laser beam scanning, the molten silicon film begins to solidify from the center.
Moreover, the silicon film on both sides in the laser beam scanning direction is fused and the heat dissipation in the lateral direction of the part to be made into a single crystal is suppressed, and the growth of polycrystals from both ends is suppressed.
A single crystallized film of extremely high quality can be obtained, and furthermore, when forming active elements such as transistors, the process can be simplified because the single crystallized film has already been separated into island shapes.

(Effects of the Invention) As described above, according to the method of manufacturing a semiconductor thin film according to the present invention, an amorphous or polycrystalline silicon film is formed in a band shape on an insulating substrate, and the band-shaped amorphous or polycrystalline silicon film is Since the laser beam is scanned in a direction intersecting the crystalline silicon film to form a single crystal, the scanning length of the laser beam on the amorphous or polycrystalline silicon becomes short, making the conditions for crystallization stable. Therefore, not only can a high-quality single crystal film be obtained, but also the single crystal thin film can be easily manufactured without adjusting the scanning position of the laser beam very precisely.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the film structure for single crystallization with a laser beam, Figure 2 is a diagram to explain the scanning situation of the laser beam, and Figure 3 is a diagram to explain the scanning situation of other laser beams. This is a diagram for 1, Insulating substrate 2, Underlayer 3, Amorphous or polycrystalline silicon film 4, Protective film

Claims (1)

[Claims] In a method for manufacturing a semiconductor thin film in which amorphous or polycrystalline silicon film formed on an insulating substrate is made into a single crystal by irradiating a laser beam to melt and solidify the amorphous or polycrystalline silicon film, the amorphous or polycrystalline silicon film is formed on the insulating substrate. 1. A method for manufacturing a semiconductor thin film, comprising forming a film in a band shape and scanning the laser beam in a direction intersecting the band-shaped amorphous or polycrystalline silicon film to convert the film into a single crystal.