1. Field of the Invention
The present invention relates to a semiconductor thin film and semiconductor device manufacturing method, and particularly to an improvement of a semiconductor thin-film formation method whereby a substantially monocrystalline silicon film can be formed in a suitable manner.
2. Description of the Related Art
Methods for manufacturing thin-film semiconductor devices whereby amorphous silicon films are heat-treated by a laser to form a polycrystalline silicon film, and the resulting polycrystalline silicon film is used as a semiconductor film to form gate electrodes and wiring on a thin metal film have been proposed for manufacturing thin-film semiconductor devices represented by polycrystalline silicon thin-film transistors (p-Si TFT) at comparatively low temperatures. With these methods, however, it is difficult to control the energy of laser, and the manufactured semiconductor films have nonuniform properties, so techniques that are free of these drawbacks and allow substantially monocrystalline silicon films to be grown have been proposed instead (see publications “Single Crystal Thin film Transistors,” IBM Technical Disclosure Bulletin, August 1993, pp. 257-258, and “Advanced Excimer-Laser Crystallization Techniques of Si Thin-Film For Location Control of Large Grain on Glass,” R. Ishihara et al, Proc. SPIE 2001, vol. 4295, pp. 14-23).
These publications disclose techniques in which a hole is formed in an insulating film on a substrate, an amorphous silicon film is formed on the insulating film and in the hole, the amorphous silicon film is irradiated by a laser, and the amorphous silicon in the bottom portions of the hole is kept in an unmelted state while the amorphous silicon film on other portions is melted, whereby crystals are grown using the amorphous silicon in the unmelted state as a crystal nucleus, and a silicon film in a substantially monocrystalline state is formed.
In the methods formed in these two publications, a plurality of crystal nuclei form in the bottom portion of the hole if the cross-section of the hole is not made sufficiently small, so expensive precision exposure devices and etching devices are needed to form a hole with such a diameter (50 nm to 150 nm).
In addition, hole formation is difficult when these devices are used to form numerous thin-film transistors on large glass substrates, as is the case with large liquid-crystal displays and the like.