Theoretical Studies on the Physical Properties of Poly-Si and Metal Gates/HfO2 Related High-k Dielectrics Interfaces

We have theoretically investigated poly-Si and metal gates on Hf-related high-k gate dielectrics. First, we have investigated the cause of the substantial threshold voltage ( V th ) shifts observed in Hf-related high- k gate stacks with p+poly-Si gates. The oxygen vacancy ( Vo ) level in ionic HfO 2 is located in a relatively higher part of the band gap. If the p+poly-Si-gate is in contact with HfO 2 , Vo formation in the HfO 2 induces a subsequent electron transfer across the interface because of the higher energy level position of Vo , causing a substantial V th shifts in p+poly-Si gate MISFETs. Next, we also investigate the microscopic electronic structures at metal gates/HfO 2 interfaces. We have found that the wave functions of metal induced gap states (MIGS) have large amplitudes both around Hf and O atoms, which may be the cause of unusual work function behaviors of p-like metals. INTRODUCTION The considerable downscaling of Si devises has brought about the requirement for a continuing need for significant reduction in gate dielectric film thickness, and even current commercial based large scale integrated (LSI) circuits have SiO