“…Over the past ten years, the integration of Hf-based high-k dielectrics, such as HfO 2 and HfSiON, and metal gate electrode materials, such as TaN, TiN, and TaSiN, have been widely studied for nanoscale CMOS devices. [1][2][3][4] Among the many high-k and metal gate integration issues, their patterning presents a critical challenge due to the low volatility of the halogendies of these new materials, which makes it difficult to achieve all required specifications such as a near vertical sidewall profile, low critical dimension (CD) gain, and high selectivity. 5,6 Meanwhile, in order to avoid these difficulties when etching thick metal gates, one popular approach is to use a gate stack with a thin metal layer inserted between a high-k dielectric and poly-Si, forming a metal inserted poly-Si stack (MIPS) structure.…”