Aluminum oxide films have been deposited on silicon substrates at low temperature (150 - 340℃) by plasma enhanced chemical vapor deposition (PECVD) using trimethyl aluminum (TMA), $N_2O$ and He gases. Metal Oxide Semiconductor (MOS) structure has been fabricated to investigate capacitance voltage (C-V) characteristics. The effects of deposition parameters on C-V characteristics of films have been investigated by C-V measurement. The chemical bonds of as-deposited films have been identified by Fourier transform infrared (FTIR) spectra.
The films deposited at the temperature of 250-340℃ have fewer O-H/$H_2O$ bonds and higher refractive index (1.55 - 1.62) than those deposited at the temperature of 150-250℃. Also, the C-V measurements show that the increase of the deposition temperature had a major effect on reducing the hysteresis of C-V curve and shifting flat band voltage to positive voltage. The increase of RF power caused shifting flat band voltage to negative voltage due to inducing positive fixed oxide charge.
The experimental results show that aluminum oxide films deposited at the high temperatures (250-340℃), low RF power densities (0.04-0.09 W/$cm^2$) and proper reactant gas composition ($N_2O$/TMA$\coug 6$) have stable properties for gate oxide in MOS structure.
