High-/Metal–Gate Stack and Its MOSFET Characteristics

Abstract—We show experimental evidence of surface phonon scattering in the high- dielectric being the primary cause of channel electron mobility degradation. Next, we show that midgap TiN metal–gate electrode is effective in screening phonon scattering in the high- dielectric from coupling to the channel under inversion conditions, resulting in improved channel electron mobility. We then show that other metal–gate electrodes, such as the ones with n+ and p+ work functions, are also effective in improving channel mobilities to close to those of the conventional SiO 2 /poly-Si stack. Finally, we demonstrate this mobility degra-dation recovery translates directly into high drive performance on high- /metal–gate CMOS transistors with desirable threshold voltages. Index Terms—Atomic layer deposition (ALD), CMOS transis-tors, Hafnium Oxide (HfO2), high- dielectric, metal–gate elec-trode, remote phonons