ZONE-MELTING RECRYSTALLIZATION OF POLYSILICON BY A FOCUSED-LAMP WITH UNSYMMETRIC TRAPEZOIDAL POWER DISTRIBUTION

Abstract

Unsymmetric trapezoidal power distribution produced by a tungsten halogen lamp and a focusing mirror has been employed in zone-melting recrystallization of polysilicon. Focusing mirror is designed based on the ray-tracing method. Experimental results show that the trapezoidal type power distribution is superior to the Gaussian type which is obtained with a conventional strip heater, in that the controllability and reproducibility are significantly improved while the recrystallized film shows comparable or slightly better crystal quality. It has been found that a lower thermal gradient at the liquid-to-solid interface under a lower scan speed improves the quality of the recrystallized film prepared by the trapezoidal power distribution.