Surface NH 3 anneal on strained Si 0.5Ge 0.5 for metal-oxide-semiconductor applications with HfO 2 as gate dielectric

Abstract

In this Letter, metal-oxide-semiconductor capacitors were fabricated and characterized on compressively strained Si50 Ge50 on Si0.8 Ge0.2 virtual substrates by using metal-organic chemical vapor deposition Hf O2 as gate dielectric and TaN as metal gate electrode. It is demonstrated that surface nitridation treatment using N H3 annealing prior to Hf O2 deposition effectively prevents the growth of Ge Ox at the interfacial layer which exists on SiGe surface with direct deposition of Hf O2. X-ray photoelectron spectroscopic analysis suggests that the nitridation process tends to occur to Si atoms rather than to Ge atoms and results in the formation of an interfacial layer of Si Nx Oy on the SiGe surface. Capacitors with the surface nitridation treatment show good capacitance-voltage characteristics with negligible hysteresis, much smaller interface trap charge density, and significantly improved gate leakage current in comparison with those of capacitors made without nitridation treatment. The surface nitridation seems to be a promising method for the formation of high quality high- κ gate stack on strained SiGe substrate. © 2006 American Institute of Physics.