Diffusion barrier for polysilicon gate electrode of mos device in

Abstract

A uniformly doped polysilicon gate electrode of an MOS device forming a part of an integrated circuit structure on a semiconductor substrate is formed by first depositing a very thin layer of amorphous or polycrystalline silicon, e.g., from about 2 nm to about 10 nm, over a gate oxide layer. The thin layer of silicon layer is then exposed to a nitrogen plasma formed from N.sub.2 at a power level sufficient to break the silicon--silicon bonds in the thin layer of silicon, but insufficient to cause sputtering of the silicon to cause a barrier layer of silicon and nitrogen to form at the surface of the thin silicon layer. Further silicon, e.g., polysilicon, is then deposited over the barrier layer to the desired thickness of the polysilicon gate electrode. The gate electrode is then conventionally doped, i.e., by implantation followed by furnace annealing, to diffuse and activate the dopant in the polysilicon gate electrode without, however, resulting in penetration of the dopant through the barrier layer into the underlying gate oxide layer or the semiconductor substrate.