Technique for low-temperature formation of excellent silicided &agr;-si gate structures

Abstract

This application relates to a process to suppress the impurity diffusion through gate oxide on silicided amorphous-Si gate structures that utilize the silicide layers as the implantation barrier to minimize the impurity diffusion by reducing the projectile range and implant-induced defects, resulting in smaller flat-band voltage(V,) shift and better characteristics of the breakdown field(E,) and charge to breakdown(Q,). In addition, the amorphous-Si underlying layer is simultaneously kept during the formation of a low-temperature self-aligned silicide (SAD) process to further retard the impurity diffusion. Hence, the usage of such bilayered silicide/amorphous-Si films could effectively retard the impurity diffusion, by combining both effects of the amorphous-Si layer and the silicide process or inducing other undesirable effects such as the increase of gate sheet resistance.