Laser irradiation method and method for manufacturing crystalline semiconductor film

A method for manufacturing a semiconductor device comprising:

• forming a crystal grain grown continuously in a scanning direction by irradiating a crystalline semiconductor film formed over a substrate having a refractive index n and a thickness d with a laser beam emitted from a pulsed laser oscillator while scanning the substrate in the scanning direction so as to improve crystallinity of the crystalline semiconductor film,
• wherein the laser beam has a pulse width t that satisfies an inequality ct<2nd where c is a speed of light in vacuum.

A method for manufacturing a semiconductor device comprising:

• forming a crystal grain grown continuously in a scanning direction by irradiating a crystalline semiconductor film formed over a substrate having a refractive index n and a thickness d with a laser beam emitted from a pulsed laser oscillator while scanning the substrate in the scanning direction so as to improve crystallinity of the crystalline semiconductor film,
• wherein the laser beam has a pulse width t that satisfies an inequality ct<4nd where c is a speed of light in vacuum.

A method for manufacturing a semiconductor device comprising:

• forming a crystal grain grown continuously in a scanning direction by irradiating a crystalline semiconductor film formed over a substrate having a refractive index n and a thickness d with a laser beam emitted from a pulsed laser oscillator while scanning the substrate in the scanning direction so as to improve crystallinity of the crystalline semiconductor film,
• wherein one point in the crystalline semiconductor film is irradiated simultaneously with both the laser beam being incident thereinto and the laser beam reflected on a rear surface of the substrate for a time corresponding to 10% or less of a pulse width of the laser beam.