Method of manufacturing a thin film transistor and a method of evaluating a polysilicon film

A method of manufacturing a thin-film transistor, in which a laser annealing apparatus anneals an amorphous silicon film and converts the amorphous silicon film to a polysilicon film that serves as a channel layer, said method comprising the steps of:

• forming a metal pattern on a substrate;
• forming an amorphous silicon film on the substrate, thereby covering the metal pattern;
• performing laser annealing on a plurality of parts of the amorphous silicon film formed on one or more substrates at different energy densities of a laser beam, thereby forming a polysilicon film;
• evaluating, in numerical value, a surface spatial structure of a part of the polysilicon film that lies above the metal pattern;
• evaluating, in numerical value, the surface spatial structure of other parts of the polysilicon film;
• calculating a difference between the numerical value of the part of the polysilicon film that lies above the metal pattern and the numerical value of the other parts of polysilicon film;
• and
• controlling the energy density of the laser beam or the thickness of the polysilicon film by using the calculated difference as a control parameter for controlling the energy density and the thickness of the polysilicon film,
• wherein linearity and/or periodicity of the surface spatial structure of the part of the polysilicon film that lies above the metal pattern is evaluated in a numerical value, and a linearity and/or periodicity of the surface spatial structure of the other parts of the polysilicon film is evaluated in a numerical value.