Study on Laser Crystallization Process in Semiconductor

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1) A numerical calculation algorism has been developped to solve the nonlinear heat equation including the temperature dependences of optical constant, themal conductivity and diffusivity, based on the linear solution of heat equation in a semi-infinite multilayer structure.2) An effective temperature, denoting the absorption rate of latent heat, has been intriduced to include the latent heat on phase transition between solid and liquid to the nonlinear numerical calculation algorism. If the effective temperature is between 1412゜C and 2857゜C, it means a partial melting. If it is above 2857゜C, then it means a melting.3) The numerical calculation results have been compared with the experimental results on melting width in Si/SiO_2/Si. It is found that the melting occurs effectively at the effective temperature of 2100゜C corresponding to the absorption of half a latent heat.4) By using a microscopic infrared camera, the radiation images have been observed to distinguish the boundaries between solid and liquid and recorded by VTR.5) A digital image input/output instrument has been made to process the images recorded by the VTR. It is found that there are mixtures of solid and liquid and that the part of solid is the nucleation center of crystallization.6) It is found that the mixtures of solid and liquid are strongly influenced by the intensity distribution of irradiating laser; that is, the temperature distribution. At the present moment, it is not clear what dominates over the physical mechanism on mixtures of solid and liquid. On this problem further investigation is needed.