Dimensional constraints and percolation theory: physical mechanisms controlling electronic structure and defects in high‐k transition metal oxide dielectrics

Abstract

AbstractThis article addresses three different aspects of nano‐scale structure that are important for the implementation of high‐k gate dielectrics, such as HfO2 and Hf Si oxynitride alloys, for advanced gate stack applications ultra large scale integrated (ULSI) circuit and system chips. Two of these deal with nano‐crystalline thin films where it is necessary to make a distinction between the primitive unit cell, and a more extended electronic cell that can support cooperative Jahn‐Teller distortions. The final example relates the bonding coordination of group IVB transition metal (TM) atoms, Ti, Zr and Hf in a ternary composition in which the concentration of four‐fold coordinated TM atoms is above a critical percolation threshold. This is critical for strain relief, thereby promoting low densities of electronically‐active defects. X‐ray absorption spectroscopy studies play a significant role in revealing these important aspects of nano‐structure, and are interpreted with in the frame‐work of many‐electron electronic structure theory. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)