JPH06163408A - Crystallizing method for semiconductor thin film - Google Patents

Abstract

PURPOSE:To form a single crystal of a polysilicon thin film ranging over a wider area. CONSTITUTION:A polysilicon thin film 2 is deposited on the upper surface of an insulating substrate 1, and when an excimer laser is applied, a polysilicon thin film 3, which is somewhat single-crystallized, is formed by recrystallizing a certain region of the polysilicon thin film 2. Then, a polysilicon thin film is deposited again on the upper surface of the somewhat single-crystallized polysilicon thin film 3, and when an excimer laser is supplied, both polysilicon thin films 3 and 4 are recrystallized using the somewhat single-crystallized polysilicon thin film 3 as a nucleus, and a polysilicon thin film 5, which is single-crystallized over a wide range of area, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor thin film crystallization method.

[0002]

2. Description of the Related Art For example, in the technical field of thin film transistors, a polysilicon thin film is formed on an insulating substrate made of glass or the like, and this polysilicon thin film is recrystallized by laser annealing to be single-crystallized over a wide range. A polysilicon thin film having grain may be formed.

[0003]

However, in the conventional crystallization method for such a semiconductor thin film, the polysilicon thin film is single-crystallized only to a certain extent, and such a polysilicon thin film is used as an active layer. There is a problem in that a large mobility cannot be obtained when a thin film transistor for use is manufactured. An object of the present invention is to provide a method for crystallizing a semiconductor thin film having grains that have been single-crystallized over a wider range.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a polysilicon thin film formed on an insulating substrate is recrystallized by laser annealing to form a polysilicon thin film having grains that have been monocrystallized to some extent. A further polysilicon thin film is deposited on the polysilicon thin film, and both the polysilicon thin films are irradiated with a laser to recrystallize with the polysilicon thin film as a nucleus.

[0005]

According to the present invention, since the polysilicon thin film having the grains which have been monocrystallized to some extent is re-crystallized, the polysilicon thin film having the grains crystallized over a wider range is formed. be able to.

[0006]

1 (A) to 1 (D) show respective steps of a semiconductor thin film crystallization method according to an embodiment of the present invention. Therefore, the crystallization method of the semiconductor thin film will be described with reference to these drawings in order.

First, as shown in FIG. 1A, a polysilicon thin film 2 is deposited on the upper surface of an insulating substrate 1 made of glass or the like, and then an excimer laser is irradiated to recrystallize the polysilicon thin film 2, As shown in FIG. 1 (B), a polysilicon thin film 3 having a grain size that is somewhat large is formed. Each grain of the polysilicon thin film 3 is single-crystallized over a wide range to some extent. next,
As shown in FIG. 1C, when a polysilicon thin film 4 is deposited again on the upper surface of the polysilicon thin film 3 and then an excimer laser is irradiated, both polysilicon thin films 3 and 4 are re-repeated with the polysilicon thin film 3 as a nucleus. By crystallizing,
As shown in FIG. 1D, a polysilicon thin film 5 having a larger grain size is formed. Each grain of the polysilicon thin film 5 is single-crystallized over a wider range.

As described above, according to this semiconductor thin film crystallization method, the polysilicon thin film 5 having single-crystallized grains over a wider range can be obtained.
Therefore, when forming a thin film transistor having such a single-crystallized polysilicon thin film 5 as an active layer, a large mobility can be obtained.

The polysilicon thin film 2 formed first on the insulating substrate 1 in the above-described embodiment may be formed by depositing an amorphous silicon thin film and forming a polysilicon thin film by laser annealing or the like.

[0010]

As described above, according to the present invention, since the polysilicon thin film having the grains that have been monocrystallized to some extent is re-crystallized, the grains that have been monocrystallized over a wider range are obtained. It is possible to form a polysilicon thin film having

[Brief description of drawings]

1A to 1D are cross-sectional views showing respective steps of a method of crystallizing a semiconductor thin film according to an embodiment of the present invention.

[Explanation of symbols]

 1 Insulating substrate 2 Polysilicon thin film 3, 4, 5 Polysilicon thin film

Claims (1)

[Claims] 1. A poly-silicon thin film formed on an insulating substrate is recrystallized by laser annealing to form a poly-silicon thin film having grains that have been mono-crystallized to some extent. A method of crystallizing a semiconductor thin film, comprising depositing a silicon thin film and irradiating both the polysilicon thin films with a laser to re-crystallize the polysilicon thin films as nuclei.