A Study on Thermal Stability of CoSi2 Employing Novel Fine-Grained Polycrystalline Silicon/CoSi2/Si(001) System

Abstract

The cobalt silicide/fine-grained polycrystalline silicon (poly-Si) structure has been employed as gate electrodes in silicon-based very large-scale integration circuits. We have constructed a novel fine-grained poly-Si/cobalt silicide/silicon (001) structure to investigate the thermal stability of cobalt silicide at elevated temperatures. The dissociated cobalt atoms are observed to diffuse from fine-grained poly-Si/cobalt silicide and cobalt silicide/silicon (001) interfaces into the fine-grained poly-Si layer through poly-Si grain boundaries and the bulk cobalt silicide layer. The dissociated Si atoms at the cobalt silicide/silicon (001) interface are observed to grow epitaxilly on the silicon (001) substrate. This observation is consistent with previous results for circuits that employed amorphous Si instead of fine-grained poly-Si.