JPH0382014A - Manufacture of semiconductor thin-film - Google Patents

Abstract

PURPOSE:To obtain an excellent semiconductor thin-film single crystal, and to change a semiconductor thin-film into a single crystal while insularly isolating the semiconductor thin-film by making the beam intensity of both side sections in the direction of the scanning of laser beams stronger than a central section and turning the central section into the single crystal while melting an amorphous or polycrystalline silicon film in the direction of scanning. CONSTITUTION:In the manufacture of a semiconductor thin-film in which an amorphous or polycrystalline silicon film formed onto an insulating substrate is converted into a single crystal by irradiating the polycrystalline silicon film with laser beams and melting and solidifying the polycrystalline silicon film, the beam intensity of both side sections in the direction of the scanning of laser beams is made stronger than a central section, and the central section is changed into the single crystal while both side sections in the direction of the scanning of laser beams of the amorphous or polycrystalline silicon film are melted. The amorphous silicon layer is formed onto a glass substrate hardly containing sodium ions in thickness of approximately 0.05-2mum through a plasma CVD method, a silicon oxide film, etc., functioning as a cap layer is shaped onto the amorphous silicon layer, and the silicon oxide film is irradiated with said laser beams and melted and solidified and turned into the single crystal.

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. Various attempts have been made to obtain high quality single crystal films of polycrystalline or amorphous silicon using this laser beam crystallization method.

For example, in Japanese Patent Application Laid-Open No. 58-21319, the beam shape of a continuous wave argon laser is made into a donut shape,
By making the intensity distribution of the laser beam a so-called bimodal type, the central part of the scanning line of the laser beam can be cooled quickly, and
It has been proposed to slowly cool both parts of the laser beam scanning line, thereby growing the single crystal from the central part to both sides of the laser beam scanning line, thereby forming a high-quality, large-sized thin film single crystal. ing.

However, this conventional semiconductor thin film manufacturing method is unstable under certain conditions, and there are cases where grain boundaries run in the center. In other words, silicon has good thermal conductivity, so even if assimilation starts from the center of the laser beam scanning line, cooling and solidification will begin from both ends by the time the laser beam reaches between the two ends.In this case, the solidification will start from the center. However, since the solid solution interface (the interface between the part where the laser beam passed and the part where it did not pass) is polycrystalline or amorphous at both ends, the single crystal does not grow. The width of the polycrystalline parts at both ends, where the grown polycrystal and the single crystal grown from the center collide, is determined by many complicated parameters such as laser power, laser beam intensity distribution, and the thickness of the silicon group. They are intertwined, making them conditionally unstable.

On the other hand, in JP-A No. 59-210638, on an insulating material,
After forming a polycrystalline, amorphous, or amorphous semiconductor film,
It has been proposed that this semiconductor film be separated into islands using a conventional photolithography technique and then irradiated with a laser beam to completely form a single crystal in a small area unit.

However, in this conventional method for manufacturing a semiconductor thin film, the number of steps increases because the semiconductor film is separated into islands before irradiating the semiconductor thin film with a laser beam.

(Objective of the Invention) The present invention was devised in view of the problems of the prior art, and is capable of producing high-quality semiconductor thin films without grain boundaries running through the center of the semiconductor thin film irradiated with a laser beam. It is an object of the present invention to provide a method for manufacturing a semiconductor thin film, which can obtain a semiconductor thin film single crystal, and can simultaneously separate the semiconductor thin film into single crystals and island shapes.

(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 group. In the method for manufacturing a semiconductor thin film which is made into a single crystal by making the beam intensity on both sides in the scanning direction of the laser beam stronger than the central part, A method for manufacturing a semiconductor 'fsM' is provided, which is characterized in that the central portion is made into a single crystal while being fused, thereby achieving the above object.

(Function) With the above configuration, after the laser beam scans, the molten semiconductor thin film begins to solidify at the center, but the two sides are fused and the semiconductor thin film is torn off, suppressing heat dissipation in the lateral direction. At the same time, the growth of polycrystals that have an adverse effect from both sides is suppressed, and the entire surface becomes a single crystal.

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

Figure 1 (ω is a diagram showing the intensity distribution of the laser beam,
FIG. 1 is a top view of a semiconductor thin film irradiated with a laser beam.

In the method for manufacturing a semiconductor thin film according to the present invention, a laser beam is used in which the beam intensity on both sides of the laser beam in the scanning direction is twice or more stronger than that at the center. However, since it varies depending on the scanning speed of the laser beam and the thickness of the film to be single-crystallized, the beam intensity at both side portions may be about 1.5 times that at the central portion. The beam intensity at the center of the laser beam in the scanning direction may be sufficient to heat and melt the semiconductor thin film.

A laser beam with such an intensity distribution can be produced by, for example, splitting a single laser beam with a Fresnel lens to form a so-called bimodal beam shape, and then passing it through an aperture to cut the base portions on both sides of the bimodal shape. By doing so, both ends of the beam are made steeper, and finally, an ND filter is applied to the center of the beam to form a beam shape having an intensity distribution as shown in FIG. 1(a), for example. In this case, the width of the central part is about 10 to 100 μm, and the width of both ends is about 1 to 100 μm.
The beam shape is shaped to be about 30 μm.

Note that this laser beam has a power of 0.5 to 20W.
A continuous wave argon laser or the like is preferably used, and scanning is performed at a scanning speed of, for example, about 1 to 20 cm/sec.

In the method for manufacturing a semiconductor thin film according to the present invention, an amorphous silicon layer is formed to a thickness of 0.05 mm by plasma CVD, for example, on a glass substrate containing almost no sodium ions.
A silicon oxide film (Sin2) is formed to a thickness of about 2 μm and acts as a so-called cap layer on this amorphous silicon layer.
etc. is formed and irradiated with the laser beam as described above to melt and solidify to form a single crystal.

In addition, it is possible to form not only an amorphous silicon layer but also a polycrystalline silicon thin film on a quartz substrate by, for example, the L P CV D method, and melt the polycrystalline silicon layer by irradiating the laser beam as described above.・It may be solidified to form a single crystal.

Note that by scanning a laser beam in a lattice pattern over an amorphous or polycrystalline semiconductor, it is also possible to form 1ψ crystallized regions separated in a lattice pattern. When viewed from above, the crystallized region can also be formed into a large number of islands having a hexagonal or other polygonal shape.

(Effects of the Invention) As described above, according to the method for manufacturing a semiconductor thin film according to the present invention, the beam intensity at both sides in the scanning direction of the laser beam is made stronger than at the center, and the amorphous or polycrystalline film at both ends is Since the silicon film is melted in the scanning direction of the laser beam and the central part is made into a single crystal, after the laser beam scans, the molten semiconductor thin film begins to solidify from the central part.
However, in the area on the image side in the laser beam scanning direction, the silicon thin film is fused and heat dissipation in the lateral direction is suppressed6, and the growth of polycrystals from both end sides is significantly suppressed. It becomes possible to provide an innovative WI manufacturing method for a semiconductor thin film in which most parts can be single-crystalized over a wide area.

Furthermore, it is possible to separate the semiconductor thin film into islands at the same time that the semiconductor thin film is single-crystalized by scanning the laser beam, which is extremely advantageous in simplifying the process when forming active elements such as transistors.

[Brief explanation of drawings]

Figure 1 (ω is a diagram showing the intensity distribution of the laser beam used in the method of manufacturing a semiconductor thin film according to the present invention, Figure 1 (O is the same (top view of the semiconductor thin film to be made into a single crystal). 〉 − Figure C

Claims (1)

[Claims] In a method for manufacturing a semiconductor thin film in which an amorphous or polycrystalline silicon film formed on an insulating substrate is irradiated with a laser beam and melted and solidified to form a single crystal, the beam intensity on both sides in the scanning direction of the laser beam 1. A method for manufacturing a semiconductor thin film, comprising: making the amorphous or polycrystalline silicon film stronger than the central portion, and converting the central portion into a single crystal while melting both portions of the amorphous or polycrystalline silicon film in the scanning direction of a laser beam.