In-situ surface passivation and metal-gate/high-k dielectric stack formation for N-channel gallium arsenide metal-oxide-semiconductor field-effect transistors

Abstract

We demonstrate an in-situ surface passivation technique for the formation of high-permittivity gate dielectric on GaAs using a multiple chamber metal-organic chemical vapor deposition (MOCVD) system. In-situ vacuum annealing and SiH4 treatment were performed prior to high-k dielectric deposition. This novel passivation scheme effectively suppresses the formation of Ga or As oxide during the high-k dielectric deposition process. Self-aligned GaAs MOSFETs were fabricated, showing excellent device characteristics with a peak electron mobility of 1244.4 cm2/Vs. The effect of post deposition anneal (PDA) temperature and forming gas anneal (FGA) conditions on the GaAs MOS capacitors was also investigated. Using HfAlO as gate dielectric, the in-situ surface passivated GaAs MOS capacitors demonstrate low frequency dispersion, small hysteresis and low midgap interface state density (D it) of 2.4 × 1011 to 7.5 × 1011 cm-2.eV-1, determined by high frequency conductance method. © 2008 IEEE.