High Performance Metal Gate CMOSFETs with Aggressively Scaled Hf-Based High-k

Abstract

The optimization of MOSFET performance with Hf-based high-k and TiN metal gate is discussed. MOSFET performance and mobility of metal and poly gate on both high-k and SiO2 are compared. Optimization of the thickness and composition of Hf-silicate is discussed in terms of charge trapping and boron diffusion. The effect of metal gate thickness is also investigated. Appropriate dry and wet etch processes are found to effectively eliminate the metal foot and high-k undercut. Impressive Ion- Ioff characteristics have been achieved by applying an optimized gate-first CMOS flow to the high-k/metal stack. Ion = 1100µA/µm and 540µA/µm was attained for N and PMOSFETs with Vdd = 1.2V and Ioff = 100nA/µm.