Method of crystallizing amorphous silicon and device fabricated using the same

Abstract

A method of crystallizing amorphous silicon includes forming an amorphous silicon film over a substrate, crystallizing the amorphous silicon film to form a polycrystalline silicon film using a sequential lateral solidification crystallization method, and performing a surface treatment to the polycrystalline silicon film, wherein the sequential lateral solidification crystallization method includes at least a first application of a first laser beam having a first energy density that completely melts a first uncrystallized portion of the amorphous silicon film and melts a first crystallized portion of the amorphous silicon film, and the surface treatment includes application of a second laser beam having a second energy density that partially melts an entire surface of the polycrystalline silicon film.

What is claimed is:  
     
         1 . A method of crystallizing amorphous silicon, comprising: 
 forming an amorphous silicon film over a substrate;    crystallizing the amorphous silicon film to form a polycrystalline silicon film using a sequential lateral solidification crystallization method; and    performing a surface treatment to the polycrystalline silicon film,    wherein the sequential lateral solidification crystallization method includes at least a first application of a first laser beam having a first energy density that completely melts a first uncrystallized portion of the amorphous silicon film and melts a first crystallized portion of the amorphous silicon film, and the surface treatment includes application of a second laser beam having a second energy density that partially melts an entire surface of the polycrystalline silicon film.    
     
     
         2 . The method according to  claim 1 , wherein the application of the first laser beam that completely melts the first uncrystallized portion of the amorphous silicon film forms a plurality of seeds along border regions between solid and liquid phases of the amorphous silicon.  
     
     
         3 . The method according to  claim 2 , wherein the first uncrystallized portion of the amorphous silicon is crystallized within a second region along a direction from the border regions toward a center portion of the first uncrystallized region using the plurality of seeds as nucleation cites during the application of the first laser beam.  
     
     
         4 . The method according to  claim 3 , wherein the second region includes a plurality of first sub-grains having a first size and a plurality of first sub-grain boundaries.  
     
     
         5 . The method according to  claim 4 , wherein the sequential lateral solidification crystallization method includes at least a second application of the first laser beam that grows the first sub-grains to form a plurality of second sub-grains having a second size greater than the first size.  
     
     
         6 . The method according to  claim 5 , wherein a first group of the second sub-grains grow along a first direction to contact a second group of the second sub-grains that grow along a second direction substantially opposite to the first direction, and wherein the first and second groups of second sub-grains form a second sub-grain boundary.  
     
     
         7 . The method according to  claim 6 , wherein the plurality of first sub-grain boundaries are disposed among the plurality of first sub-grains and among the plurality of second sub-grains, and wherein the plurality of first sub-grain boundaries and the second sub-grain boundary include a plurality of particles.  
     
     
         8 . The method according to  claim 7 , wherein the application of the second laser beam partially melts and re-crystallizes the polysilicon film and removes the plurality of particles.  
     
     
         9 . The method according to  claim 8 , wherein the surface treatment maintains polycrystalline characteristics of the plurality of second sub-grains.  
     
     
         10 . The method according to  claim 9 , wherein the surface treatment forms a new grain boundary within a region where the first and second groups of second sub-grains directly contacts each other.  
     
     
         11 . The method according to  claim 1 , wherein the first laser beam has a beam width of about 2 to 3 micrometers.  
     
     
         12 . The method according to  claim 1 , wherein the surface treatment is performed within a vacuum chamber.  
     
     
         13 . The method according to  claim 12 , wherein the vacuum chamber includes inert gas.  
     
     
         14 . The method according to  claim 12 , wherein the vacuum chamber includes a dielectric window on a top portion of the vacuum chamber and a stage within an interior of the vacuum chamber.  
     
     
         15 . The method according to  claim 14 , wherein the dielectric window provides an air/vacuum tight seal with the vacuum chamber, and the substrate is disposed on the stage.  
     
     
         16 . The method according to  claim 12 , further comprising: 
 disposing the polycrystalline silicon film formed by the first laser beam over the stage of the vacuum chamber; and    applying the second laser beam along an entire surface of the polycrystalline silicon film disposed in the vacuum chamber.    
     
     
         17 . The method according to  claim 16 , wherein the application of the second laser beam is through the dielectric window of the vacuum chamber.  
     
     
         18 . A display device including a plurality of thin transistors formed using the method according to  claim 1 .  
     
     
         19 . A liquid crystal display panel including a plurality of thin transistors formed using the method according to  claim 1.