Effect of Using Chemical Vapor Deposition WSi2 and Postmetallization Annealing on GaAs Metal-Oxide-Semiconductor Capacitors

We report the use of chemical vapor deposition (CVD) for tungsten silicide (WSi 2 ) gate deposition on an Al 2 O 3 /GaAs substrate for the realization of III-V metal-oxide-semiconductor capacitor stacks. The as-deposited capacitor shows smooth and abrupt interfaces and exhibits good capacitance-voltage (C-V) characteristics with low frequency dispersion at flatband voltage and accumulation. A lower dielectric constant for Al 2 O 3 (K eff ∼ 6.4) is reported due to fluorine incorporation from the precursor during the CVD process. The work function of the as-deposited WSi 2 metal gate is determined to be ∼4.2 eV and increases to ∼4.4 eV after thermal annealing at 600°C as observed from the C-V measurement due to hexagonal-tetragonal WSi 2 phase transformation.