Polysilicon evaluating method, polysilicon inspection apparatus and method for preparation of thin film transistor

Abstract

The state of a polysilicon film formed by excimer laser annealing an amorphous silicon film is to be evaluated. When the amorphous silicon film is annealed to form a polysilicon film, linearity or periodicity presents itself in the spatial structure of the film surface of the polysilicon film formed depending on the energy applied to the amorphous silicon during annealing. This linearity or periodicity is processed as an image and represented numerically from the image by exploiting the linearity or periodicity. The state of the polysilicon film is checked based on the numerical results.

What is claimed is:  
     
         1 . A method for evaluating a polysilicon film formed by annealing an amorphous silicon film, comprising: 
 evaluating the linearity and/or periodicity of a spatial structure of the film surface of the polysilicon film; and    evaluating the state of the polysilicon film based on the result of evaluation of linearity and/or periodicity.    
     
     
         2 . The method for evaluating the polysilicon film according to    claim 1    wherein the polysilicon film generated on laser annealing the amorphous silicon film is evaluated.  
     
     
         3 . The method for evaluating the polysilicon film according to    claim 2    wherein the polysilicon film generated on laser annealing the amorphous silicon film with a light beam having a linear irradiating surface is evaluated.  
     
     
         4 . The method for evaluating the polysilicon film according to    claim 3    wherein the polysilicon film generated on excimer laser annealing the amorphous silicon film is evaluated.  
     
     
         5 . The method for evaluating the polysilicon film according to    claim 1    wherein an image on the film surface of said polysilicon film is photographed and linearity and/or periodicity of a spatial structure of the film surface is evaluated from the autocorrelation of said image.  
     
     
         6 . The method for evaluating the polysilicon film according to    claim 1    wherein the UV laser is illuminated on said polysilicon film to photograph an image of said polysilicon film and evaluation is made of the linearity and/or periodicity of the spatial structure of the photographed surface image of the polysilicon film.  
     
     
         7 . An apparatus for inspecting a polysilicon film formed by annealing an amorphous silicon film, comprising: 
 means for observing the spatial structure of the surface of said polysilicon film; and    means for evaluating the linearity and/or periodicity of the spatial structure of the film surface of said polysilicon film acquired by said observing means to inspect the state of said polysilicon film based on the result of evaluation of said linearity and/or periodicity.    
     
     
         8 . The inspection apparatus according to    claim 7    wherein said inspection means evaluates the linearity and/or periodicity of the spatial structure of the film surface of the polysilicon film generated on laser annealing the amorphous silicon film.  
     
     
         9 . The inspection apparatus according to    claim 8    wherein said inspection means evaluates the linearity and/or periodicity of the spatial structure of the film surface of the polysilicon film generated on laser annealing the amorphous silicon film with a laser beam having a linear irradiating surface.  
     
     
         10 . The inspection apparatus according to    claim 9    wherein said inspection means evaluates the polysilicon film formed by excimer laser annealing processing performed on said amorphous silicon film.  
     
     
         11 . The inspection apparatus according to    claim 7    wherein said observing means photographs an image on the film surface of said polysilicon film; and 
 wherein said inspection means evaluates the linearity and/or periodicity of the spatial structure of the film surface from the autocorrelation of the image on the film surface of said polysilicon film photographed by said observing means.  
 
     
     
         12 . The inspection apparatus according to    claim 7    wherein said observing means illuminates UV laser on said polysilicon film to observe the surface image of said polysilicon film.  
     
     
         13 . A method for preparation of a thin-film transistor, comprising the steps of: 
 forming an amorphous silicon film;    annealing the formed amorphous silicon film to form a polysilicon film; and    evaluating the linearity and/or periodicity of the spatial structure of the film surface of the polysilicon film to evaluate the state of the polysilicon film based on the result of evaluation of linearity and/or periodicity.    
     
     
         14 . The method for preparation of the thin-film transistor according to    claim 13    wherein, in said polysilicon film forming step, the amorphous silicon film is laser-annealed to form a polysilicon film.  
     
     
         15 . The method for preparation of the thin-film transistor according to    claim 14    wherein, in said polysilicon film forming step, the polysilicon film is formed by laser annealing said amorphous silicon film with a light beam having a linear irradiating surface.  
     
     
         16 . The method for preparation of the thin-film transistor according to    claim 15    wherein, in said polysilicon film forming step, the polysilicon film is formed by excimer laser annealing on an amorphous silicon film.  
     
     
         17 . The method for preparation of the thin-film transistor according to    claim 13    wherein, in said evaluating step, the surface image of the polysilicon film is photographed and the autocorrelation of the surface image is found to evaluate the linearity and/or periodicity of the spatial structure of the film surface.  
     
     
         18 . The method for preparation of the thin-film transistor according to    claim 13    wherein, in said evaluating step, the UV laser is illuminated on said polysilicon film to photograph a surface image of said polysilicon film to perform evaluation based on the photographed surface image.  
     
     
         19 . The method for preparation of the thin-film transistor according to    claim 13    wherein, in said polysilicon film forming step, the energy applied to said amorphous silicon film in said annealing is controlled depending on the results of evaluation in said evaluation step.  
     
     
         20 . A method for preparation of a thin-film transistor having a step of forming a polysilicon film serving as a channel layer by laser annealing an amorphous silicon film by an excimer laser annealing device, comprising the steps of: 
 forming a gate electrode on a substrate;    forming an amorphous silicon film on the substrate on which said gate electrode has been formed;    laser annealing said amorphous silicon films on plural substrates or plural locations of said amorphous silicon film on a sole substrate to form a polysilicon film;    evaluating the linearity and/or periodicity of a spatial structure of a surface of said polysilicon film formed on the gate electrode on said substrate;    evaluating the linearity and/or periodicity of the spatial structure of the surface of said polysilicon film formed on locations other than the gate electrode on said substrate;    calculating the manufacturing margin of said polysilicon film in the laser annealing based on the linearity and/or periodicity of said spatial structure of the polysilicon film surface formed on said gate electrode and on the linearity and/or periodicity of the polysilicon film surface formed on a location other than said gate electrode; and    setting the laser power of said excimer laser annealing device based on said manufacturing margin.    
     
     
         21 . A method for preparation of a thin-film transistor of a bottom gate structure in which a gate electrode is formed between a substrate and a polysilicon film, comprising the steps of: 
 forming a gate electrode on said substrate;    forming an amorphous silicon film on said substrate on which said gate electrode has been formed;    laser annealing said amorphous silicon film to form a polysilicon film; and    checking the acceptability of said polysilicon film based on a spatial structure of the surface of said polysilicon film;    said checking step comprising:    evaluating the linearity and/or periodicity of the spatial structure of the surface of said polysilicon film formed on said gate electrode of each substrate;    evaluating the linearity and/or periodicity of the spatial structure of the surface of said polysilicon film formed on a location other than said gate electrode of each substrate; and    checking the acceptability of said polysilicon film based on the linearity and/or periodicity of the spatial structure of the surface of said polysilicon film formed on said gate electrode or on the linearity and/or periodicity of the spatial structure of the surface of said polysilicon film formed on a location other than said gate electrode.