Perspectives paper: First principles modeling of high-k gate dielectrics

Abstract

Aggressive scaling has led to silicon dioxide (SiO₂) gate dielectrics as thin as 15 Å in state-of-the-art CMOS technologies. As a consequence, static leakage power due to direct tunneling through the gate oxide has been increasing at an exponential rate. As technology roadmaps call for sub-10 Å gate oxides within the next five years, a variety of alternative high-k materials are being investigated as possible replacements for SiO₂. The higher dielectric constants in these materials allow the use of physically thicker films, potentially reducing the tunneling current while maintaining the gate capacitance needed for scaled device operation. Recognizing that the current Si/SiO₂ system benefits from nearly 30 years of research, developing a replacement material for SiO₂ presents an immense challenge. This has prompted recent interest in novel computational approaches, such as first principles density functional theory (DFT) simulations, to computationally screen candidate dielectrics by predicting their properties based on the microscopic interactions within the system.

This paper provides perspectives on the application of DFT simulations to address challenging problems of high-k gate dielectric research. We provide background and motivation for the development of high-k materials and highlight opportunities for theoretical study of such materials. We also describe specific examples of recent first principles work related to two particularly promising materials systems: silicates and aluminates.