MINIMAL GLASS DEFORMATIONS WITH RAPID THERMAL ANNEALING CONTROL

A critical step in the fabrication of polycrystalline silicon thin-fil m transistors (TFT's) is to crystallize the amorphous silicon layer de posited on glass. This paper describes a complete rapid thermal anneal ing (RTA) process applied to the crystallization of the amorphous laye r. The RTA heating and cooling rates have been optimized to minimize t hermal gradients and to improve glass substrate stability. Numerical s imulations taking into account the lamp characteristics, the annealing chamber configuration and the sample properties have been developed a nd allow elucidation of thermal nonuniformities in the sample during t he RTA process. Although the transition point of a glass (T-g) is ofte n considered as an upper limit in usual polysilicon TFT's processes, t his paper shows that if the cooling rate is accurately. controlled, an nealing temperatures can be above T-g without thermal damage to the gl ass.