GaAs MOS Capacitors and Self-Aligned MOSFETs with HfO2 Gate Dielectrics

Abstract

Introduction: The difficulty of increasing performance by scaling in sub-100 nm Si CMOS technology has renewed interest in the use of Ill-V channel materials for advanced VLSI CMOS [1]. GaAs is an attractive choice for this application, due to its relative maturity compared to other III-Vs, its high electron mobility (6x compared to Si), and its lattice matching with Ge. The main barrier towards implementing GaAs for VLSI applications is the difficulty of forming a high-quality gate insulator [2]-[6]. However, other problems also need to be overcome, including poor thermal stability, low implant activation, and the lack of a self-aligned contacting scheme. In this work, we seek to address the integration and gate dielectric issues. We have developed a self-aligned process for GaAs MOSFETs with HfO2 gate dielectrics, and demonstrate functional enhancementand depletion-mode devices. We have also characterized MOS capacitors with GaAs/u-Si/SiO2/HfO2 gate stacks, and found that these structures have much lower DA and improved thermal stability compared to HfO2 films directly on GaAs.