Laser irradiation method and apparatus for forming a polycrystalline silicon film

Abstract

A method for changing an amorphous silicon film to a polycrystalline silicon film includes the steps of irradiating an elongate pulse laser beam onto the silicon film while scanning in the direction normal to the major axis of the elongate pulse laser beam, to form a plurality of irradiated areas, irradiating flat-surface light onto the irradiated areas in the direction parallel to the major axis, and analyzing distribution of the reflected light from the irradiated areas to determine the threshold value of micro-crystallization. The threshold value is used to further determine an energy density of the elongate pulse laser beam for the phase change process.

1 - 8 . (canceled) 
     
     
         9 . A method for determining a threshold value of a micro-crystallization energy density, comprising the steps of:
 irradiating an elongate first pulse laser beam having a specific generation frequency onto a semiconductor layer with a plurality of different energy densities while scanning in a direction normal to a major axis of said first pulse laser beam, to thereby form a plurality of first irradiated areas corresponding to said different energy densities;   irradiating a flat-surface light onto said first irradiated areas in a direction substantially parallel to said major axis of said first pulse laser beam, to receive reflected light from each of said first irradiated areas; and   analyzing said reflected light to determine a threshold value of a micro-crystallization energy density by determining a color distribution from said reflected light in a direction normal to said major axis of said first pulse laser beam.   
     
     
         10 . The method according to  claim 9 , wherein said threshold value is determined based on a periodicity of said reflected light in said determining step. 
     
     
         11 . The method according to  claim 9 , wherein said threshold value is determined by judging a distance between adjacent peaks of color change and/or uniformity of said color change. 
     
     
         12 . The method according to  claim 9 , wherein said threshold value is determined by a width of a color in said color distribution. 
     
     
         13 . A light analyzing apparatus comprising:
 a moving stage for a substrate with a semiconductor layer irradiated an elongate first pulse laser beam having a specific generation frequency onto with a plurality of different energy densities while scanning in a direction normal to a major axis of said first pulse laser beam, to thereby form a plurality of first irradiated are as corresponding to said different energy densities;   a flat-surface light source for irradiating flat-surface light in a direction parallel to said major axis of said first pulse laser beam; and   a light-sensitive device for receiving said flat-surface light reflected from the semiconductor layer, analyzing said reflected light to determine a threshold value of a micro-crystallization energy density by determining a color distribution from said reflected light in a direction normal to said major axis of said first pulse laser beam.   
     
     
         14 . The light analyzing apparatus according to  claim 13 , further comprising:
 a laser light source for generating a pulse laser beam;   an optical system for converting said pulse laser beam into an elongate first pulse laser beam; and   a moving device for scan-moving a substrate table relative to said first pulse laser beam in a direction normal to said major axis of said first pulse laser beam.