Study on advanced gate stack using high-k dielectric and metal electrode

Abstract

Metal/High-K gate stack will replace conventional poly-Si gate stack for continuous scaling of CMOS technology. In this thesis, several challenges on formation of Metal/High-K gate stacks have been discussed. Firstly, anisotropy gate stack of TaN, TiN, and HfN with high selectivity over under-laying high-k was formed. The etching and high selectivity mechanisms were explored in detail. Secondly, retard of etching rates of TaN, TiN, and HfN under the SiO2/Si3N4 hard was observed. Thirdly, ion assisted wet removal of (HfO2)x(SiON)1-x high dielectric constant materials and its effect on electrical properties were investigated. Lastly, Hafnium carbide (HfCx) is investigated as a novel metal gate electrode with good thermal stability for the first time.