SPLIT POLY-SiGe/POLY-Si ALLOY GATE STACK

摘要

A multi-layered gate electrode stack structure of a field effect transistor device is formed on a silicon nano crystal seed layer (41) on the gate dielectric (43). The small grain size of the silicon nano crystal layer allows for deposition of a uniform and continuous layer of poly-SiGe (45) with a [Ge] of up to at least 70% using in situ rapid thermal chemical vapor deposition (RTCVD). An in-situ purge of the deposition chamber in a oxygen ambient at rapidly reduced temperatures results in a thin SiO2 or SixGeyOz interfacial layer (47), (3) to 4A thick. The thin SiO2 or SixGeyOZ interfacial layer is sufficiently thin and discontinuous to offer little resistance to gate current flow yet has sufficient [O] to effectively block upward Ge diffusion during heat treatment to thereby allow silicidation of a subsequently deposited layer of cobalt. This gate electrode stack structure is used for both nFETs.and pFETs.