Extremely Short Period Melting and Solidification of Si Film in Laser Annealing and Properties of Poly-Si Film.

Abstract

Extremely short period melting and solidification of Si thin film induced by laser annealing is observed by in-situ monitoring techniques of transient reflectance and conductance measurements. The temperature evolution and resulting phase transformation are discussed based on thermodynamic analysis. It was clarified that complete melting of the Si film and following supercooling to 640 K below the melting point induce both microcrystallization and amorphization of the film. The properties of the polycrystalline Si (poly-Si) films formed by the laser annealing are investigated by means of analytical approach and measurement of electrical characteristics. The poly-Si films have high-density defects localized at grain boundary with the concentration of 1017 to 1018 cm-3. Hydrogen or oxygen plasma treatment to the films efficiently terminates the defects and lowers the density below 1 × 1017 cm-3. The combined process technology of laser annealing and plasma treatment allows us to apply the film to high-performance poly-Si thin-film transistors (TFTs).