Active solid-state devices (e.g. – transistors – solid-state diode – Non-single crystal – or recrystallized – semiconductor... – Non-single crystal – or recrystallized – material with...
Patent
1993-11-23
1996-05-14
Saadat, Mahsid
Active solid-state devices (e.g., transistors, solid-state diode
Non-single crystal, or recrystallized, semiconductor...
Non-single crystal, or recrystallized, material with...
257 56, 257 65, 257 70, 257 75, 437109, 437191, 437193, H01L 2904, H01L 31036, H01L 27108
Patent
active
055170374
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a polysilicon thin film which is fabricated on an inexpensive glass substrate or the like, and a production method therefor.
BACKGROUND ART
Polysilicon thin films have been used previously in order to simplify the manufacturing processes and reduce the manufacturing costs of thin-film transistors and thin-film solar cells. Although these polysilicon thin films can be obtained, it is not possible to use inexpensive glass substrates (usual softening point not more than 650.degree. C.) since with the prior art a temperature of not less than 650.degree. C. is required. On the other hand, with glass substrates having a high softening point, there is a problem of diffusion of impurities in the substrate into the polysilicon, and a further problem is that due to the difference in thermal expansion coefficient between the polysilicon and the glass substrate, it is difficult to deposit polysilicon onto a glass substrate.
Moreover, in order to minimize carrier recombination in the polysilicon thin film, the crystal grain diameter (below, grain size) needs to be controlled. Since the grain size of the polysilicon thin film is influenced by the substrate temperature, the grain size of polysilicon thin films is generally controlled by varying the substrate temperature. At that time, the substrate temperature is varied between 600.degree. C. and 1100.degree. C. Accordingly, for the above reason, it is not possible to control the grain size of polysilicon formed on inexpensive glass substrates. For a similar reason, it is not possible to control the grain size of polysilicon thin films formed on metal substrates.
On the other hand, in a recently proposed annealing method in which a polysilicon film is obtained by annealing an amorphous silicon film using an excimer laser, it is necessary to move the substrate or the optical system because of the small size of the laser spot. A problem here is that it is difficult to obtain a uniform polysilicon film over a large area, since either the crystallization at the boundary region is uneven or there is a remnant of the amorphous part.
Furthermore, another disadvantage concerning the control of the grain size of the polysilicon film is that, since the grain size is basically determined by the substrate temperature, it is difficult to form a product having a large grain diameter.
The present invention has been realized in consideration of these kinds of problems inherent in the prior art, and accordingly, the main object of this invention is to provide a polysilicon thin film which can be formed on an inexpensive glass substrate or metal substrate, and moreover, whose grain size can be controlled, and a production method therefor. A further object of the present invention is to provide a substrate for forming a thin polysilicon film and a production method therefor, as well as a radical source used for forming a polysilicon thin film.
DISCLOSURE OF THE INVENTION
The first mode of the present invention relates to a polysilicon thin film characterized in that it is formed on a substrate and has a particulate product of SiO.sub.x (0<x.ltoreq.2) of size not more than 100 .ANG. at the interface of the substrate with the polysilicon.
In the first mode of the present invention, it is preferred that the above-mentioned SiO.sub.x particulate product of size not more than 100 .ANG. is dispersed into not more than 100 pieces per 0.1 .mu.m square area.
In the first mode of the present invention, the SiO.sub.x particulate product preferably exists in an amorphous silicon matrix.
Furthermore, in the first mode of the present invention, it is preferable that the SiO.sub.x particulate product is formed by processing using plasma CVD of a gas mixture of a silane-series gas and an oxygen-series gas.
Here, the silane-series gas is preferably SiH.sub.4 gas, Si.sub.2 H.sub.6 gas or a gas mixture of these, and the oxygen-series gas is preferably N.sub.2 O gas, O.sub.2 gas, H.sub.2 O gas or a gas mixture of these.
In addition, it is preferred th
REFERENCES:
patent: 4719501 (1988-01-01), Nakagawa et al.
patent: 4789883 (1988-12-01), Cox et al.
patent: 4947219 (1988-08-01), Boehm
patent: 5006180 (1991-04-01), Kanai et al.
patent: 5164338 (1992-11-01), Graeger et al.
Kanegafuchi Chemical Industry Co. Ltd.
Saadat Mahsid
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