Semiconductor thin film crystallization device and semiconductor thin film crystallization method

Abstract

A first laser beam is emitted from a first laser oscillator in a pulsed manner at a high repetition frequency, and converged onto a substrate by a first intermediate optical system 2 so as to form a slit-like first beam spot. A second laser beam is emitted from a second laser beam oscillator in a pulsed manner to rise precedent to and fall subsequent to the first laser beam, and converged onto the substrate by a second intermediate optical system so as to form a second beam spot similar in configuration to the first beam spot and to contain the first beam spot. Crystallization of a semiconductor thin film on the substrate is carried out while the substrate or the first, second beam spots are moved. Thereby, the whole semiconductor thin film is formed into a crystal surface that has grown in one direction and free from ridges. Thus, the semiconductor thin film has an extremely flat surface, extremely few defects, large crystal grains and high throughput.

1 . A semiconductor thin film crystallization device comprising: 
 a first laser irradiation unit for emitting a first laser beam and forming a striped first beam spot having a specified width and a specified length on a semiconductor thin film on a substrate;    a second laser irradiation unit for emitting a second laser beam and forming a second beam spot having a shape containing the first beam spot on the semiconductor thin film; and    a relative moving unit for moving the substrate in a widthwise direction of the first beam spot relatively with respect to the two beam spots, wherein    the second laser irradiation unit emits the second laser beam at least while the first laser beam is being emitted, and maintains intensity of the second laser beam constant at a level lower than a maximum intensity of the first laser beam and during a period from an emission start time to an emission end time, and    a light intensity distribution by the second laser irradiation unit within the second beam spot is constant at least in a portion overlapping with the first beam spot.    
   
   
       2 . The semiconductor thin film crystallization device as claimed in  claim 1 , wherein 
 the specified width in the striped first beam spot is not less than 5 micron and not more than 50 microns.    
   
   
       3 . The semiconductor thin film crystallization device as claimed in  claim 1 , wherein 
 the second laser beam emitted by the second laser irradiation unit is a carbonic acid gas laser beam.    
   
   
       4 . The semiconductor thin film crystallization device as claimed in  claim 1 , wherein 
 the second laser irradiation unit emits the second laser beam in a pulsed manner.    
   
   
       5 . The semiconductor thin film crystallization device as claimed in  claim 1 , wherein 
 emission frequency of the first laser beam by the first laser irradiation unit is not less than 1 kHz and not more than 100 kHz.    
   
   
       6 . The semiconductor thin film crystallization device as claimed in  claim 1 , wherein 
 the relative moving unit is a substrate driver section on which the substrate is placed and which is enabled to move the substrate from one end portion to other end portion of the substrate in a widthwise direction of the beam spot and to rotate the substrate by 90°.