Metal/high-k Interface Interactions Upon High Temperature Annealing - Are They Cause Of Work Function Changes

摘要

The replacement of poly-silicon by metallic compounds in the gate stack leads to the search of metals with suitable work function. However, it is observed that thermal budget has a large influence on the effective work functions of several metals. In this paper, we investigated the possible modification of the chemical states by physical analysis techniques (XPS, ERD, SIMS) by studying the chemistry of the high-k oxide/metal interface. We show that in the case of the TiN/TaN/HfO{sub}2/SiO{sub}2/Si stack, several modifications occur upon 1000°C N{sub}2 annealing: Increase of the nitrogen content of the TaN, interdiffusion of the Ti and TaN, and formation of Ta{sub}2O{sub}5 at the TaN/HfO{sub}2 interface.