| The continuous size downscaling of complementary metal-oxide-semiconductor (CMOS) transistors has led to the twin-replacement of (1) SiO2 with a HfO2-based high dielectric constant (or high-k) oxide, and (2) the polysilicon electrode with a metal gate. Nevertheless, this technological evolution is accompanied by several issues, such as the high defect density, charge traps/sources within HfO2, the chemical instability of thin HfO2 layers in contact with Si, and the difficulty to control the metal Fermi level alignment to the silicon band edges. In the present work, the above problems have been addressed using density functional theory (DFT) modeling and first principles thermodynamics (FPT). Specifically, we have studied the phase equilibria at the Si/HfO2 interface, the processing-induced variation of the effective work function of the metal/HfO 2 interface and interface engineering through atomic dopants. An attempt was also made to assess the fidelity with which modern DFT and beyond-DFT methods may be used in the prediction of defect properties in non-metals found in MOSFETs (such as Si, Ge and ZrO2). First principles studies are expected to continue providing important insights to the CMOS research community for the further optimization and "scaling down" of transistors. |
