Polycrystalline silicon thin film and low temperature fabricatio

Details Polycrystalline silicon thin film and low temperature fabricatio Polycrystalline silicon thin film and low temperature fabricatio

1993-07-12

1995-02-07

Breneman, R. Bruce

Fishing, trapping, and vermin destroying

437 2, 437 4, 437173, 437233, H01L 2120

Patent

active

053875427

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a polycrystalline silicon (polysilicon) thin film fabricated on an inexpensive glass substrate and a large-area, low-temperature fabrication method thereof, having potential applications for thin film transistors and thin-film solar cells.


BACKGROUND ART

Since conventional methods for the fabrication of a polysilicon thin film require a high temperatures of more than 650.degree. C., a glass substrate with a softening point of less than 650.degree. C. is not able to be used. In order to avoid diffusion of impurities, it is necessary to use a highly pure quartz glass substrate among glass substrates with a softening point above 650.degree. C.
Recently, a low temperature method using an excimer laser has been intensively researched. In this method, however, only a small area such as 5 mm square is able to be crystallized, so that it is necessary to move the substrate in order to obtain complete crystallization over a large area. When the substrate is moved, nonuniformity of crystallization arises in the boundary region depending upon the moving speed of the substrate, so that it is difficult to uniformly form the polysilicon thin film on a large area.
The present invention is made to resolve the above-mentioned disadvantages of the conventional art, namely, it is an object of the present invention to provide a polysilicon thin film and a low temperature fabrication method thereof in which an inexpensive glass substrate such as a soda glass is used as a substrate.


DISCLOSURE OF THE INVENTION

The polysilicon thin film of the present invention is a polysilicon thin film fabricated on a glass substrate characterized in that the hydrogen content of the film is not more than 5 atomic %.
The polysilicon thin film of the present invention is preferably fabricated over the surface of a metal electrode or transparent electrode, wherein both said metal or transparent electrodes are fabricated on the surface of a glass substrate. Furthermore, the thin polysilicon film is preferably fabricated using repetitions comprising the successive fabrication of amorphous silicon film by the CVD method or PVD method, exposure of the film to hydrogen plasma for a set period of time, and fabrication of further amorphous silicon film.
Moreover, in the present invention, it is preferable that the hydrogen plasma is generated by ECR discharge using permanent magnets, and that pressure thereof is not more than 100 mTorr.
The method of the present invention is a method fabricating a polysilicon film on a glass substrate characterized in that the polysilicon film is formed at a temperature not more than 400.degree. C.
In addition, the fabrication method of the present invention preferably comprises multiple repetitions of a process comprising the fabrication of an amorphous silicon film by the CVD method or PVD method or and subsequent exposure of the amorphous silicon film to a hydrogen plasma for a set period of time.
Moreover, in the method of the present inventions, it is preferable that the above-mentioned CVD method or PVD method and the exposure to hydrogen plasma are carried out in the same chamber.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a film forming apparatus applied to the film fabrication method of the present invention;
FIG. 2 is the Raman spectrum of an embodiment of the present invention; and
FIG. 3 is the X-ray diffraction spectrum of an embodiment of the present invention.


BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter the present invention is described on the basis of an embodiment, however, the scope of the present invention is not limited to the embodiment.
As a substrate for fabrication of the thin polysilicon film, insulating substrates such as glass quartz, sapphire and so on, or these substrates on which transparent electrodes such as TiO.sub.2, SnO.sub.2 and so on are formed can be used.
However, of these substrates, a glass substrate is preferable because of its lower cost, and in particular, an inexpensive soda glass s

REFERENCES:
patent: 4358326 (1982-11-01), Doo
patent: 4664937 (1987-05-01), Ovshinsky
patent: 4741964 (1988-05-01), Haller
patent: 4762803 (1988-08-01), Sato et al.
patent: 5221643 (1993-06-01), Griep

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