Laser annealing device and method for producing thin-film transistor

A laser annealing method for annealing a substance formed on a major surface of a substrate, by illuminating the laser light on the surface of said substance, comprising:

• a time interval as from a timing of radiating the laser light of one pulse to the surface of said substance until a timing that the temperature of the substrate raised as a result of the illumination of the one pulse of the laser light on the surface of said substance reverts to an original temperature of the substrate, being a reference period,
• radiating the laser light in a pulsed fashion with a period shorter than said reference period;
• and
• controlling the illuminated position of said laser light radiated in the pulsed fashion from said laser light radiating unit on the surface of said substance so that the laser light is illuminated a plural number of times on the same position on the surface of said substance.

A method for producing a thin film transistor having a polysilicon film, comprising:

• a laser annealing step of illuminating laser light on an amorphous silicon film formed on a substrate for annealing said amorphous silicon film for transforming said amorphous silicon film into a polysilicon film;
• in said laser annealing step radiating pulses of said laser light to a surface of said amorphous silicon film at a period shorter than a reference period, said reference period being a time interval as from a timing of radiating the laser light of one pulse to the surface of said substance until a timing that the temperature of the substrate raised as a result of the illumination of the one pulse of the laser light on the surface of said substance reverts to an original temperature of the substrate;
• and
• in said laser annealing step controlling the illuminating position of said laser light on the surface of said amorphous silicon film so that said laser light radiated in a pulsed fashion is radiated a plurality of numbers of times on the same position on the surface of said amorphous silicon film.

A method for manufacturing a thin-film transistor of a bottom gate structure, comprising:

• a film forming step of forming an amorphous silicon film on a substrate;
• and
• a polysilicon film forming step of forming a polysilicon film by illuminating a laser light beam on the resulting amorphous silicon film;
• wherein in said film forming step, the film thickness of said amorphous silicon film is controlled, depending on the wavelength of the laser light beam, so that the transmittance of the laser light beam is not less than 2% and not larger than 20%.

An apparatus for manufacturing a thin-film transistor of a bottom gate structure, comprising:

• a film forming unit for forming an amorphous silicon film on a substrate;
• a laser oscillating unit for oscillating a laser light beam;
• and
• a laser illuminating unit for illuminating the oscillated laser light beam on said amorphous silicon film,
• wherein,
• said film forming unit controlling the film thickness of said amorphous silicon film, depending on the wavelength of said laser light beam, so that the transmittance of said laser light beam is not less than 2% and not larger than 20%.