Reliability Of Ultra-thin Titanium Dioxide (tio_2) Films On Strained-si

摘要

Ultra-thin high-k titanium oxide (equivalent oxide thickness -2.2 nm) films have been deposited on strained-Si/relaxed-Si_(0.8)Ge_(0.2) heterolayers using titanium tetrakis iso-propoxides (TTIP) as an organometallic source at low temperature (<200 ℃) by plasma enhanced chemical vapor deposition (PECVD) technique in a microwave (700 W, 2.45 GHz) plasma cavity discharge system at a pressure of 66.67 Pa. The trapping/ detrapping behavior of charge carriers in ultra-thin TiO_2 gate dielectric during constant current (CCS) and voltage stressing (CVS) has been investigated. Normalized trapping centroid and trapped charge density variation with injected fluences have been investigated and also empirically modeled. Oxide lifetime is predicted using empirical reliability model developed. Dielectric breakdown and reliability of the dielectric films have been studied using constant voltage stressing. A high time-dependent dielectric breakdown (TDDB, t_(bd) >1000 s) is observed under high constant voltage stress.