High-k/Metal Gates- from research to reality

Miniaturization of the Si MOSFET required in order to attain higher transistor performance and greater economies of scale have spurred the need for significant materials innovations. This is most apparent in the search for the ideal high-k/metal gate stack as replacement for conventional SiON/Poly-Si gate stacks. In this paper, some of the key advances that have made high-k/metal gate stacks a reality will be reviewed. The innovations included optimized metal and interfaces for improved electron mobility in HfO₂/metal gate stacks and insertion of nanoscale gp. IIA and IIIB elements layers between the HfO₂ and metal electrode stack for band-edge nMOSFETs. Significant hurdles prevented similar solutions for pMOSFET stacks, primarily due to the presence of thermally activated point defects. However, by careful engineering optimization, pMOSFETs have also been realized, resulting in scalable high performance CMOS using High-k/metal gate stacks.