Study of the effect of thermal annealing on high k hafnium oxide thin film structure and electrical properties of MOS and MIM devices

The effect of rapid thermal annealing on structural and electrical properties of high k HfO2 thin films is investigated. The films were initially deposited at pre-optimized sputtering voltage of 0.8 kV and substrate bias of 80 V in order to get optimized results for oxide charges and leakage current as a MOS device. The film properties were investigated for optimum annealing temperature in oxygen and optimum rapid thermal annealing temperature in nitrogen respectively to get the best electrical results as a MOS device structure. The film thickness, composition and microstructure is studied by Laser Ellipsometry, XRD and AFM and the effect of thermal annealing is shown. The electrical I-V and C-V characteristics of the annealed dielectric film were investigated employing Al-HfO2-Si MOS capacitor structure. The flat-band voltage (V (fb)) and oxide-charge density (Q (ox)) were extracted from the high-frequency C-V curve. Dielectric study were further carried out on HfO2 thin films having metal-insulator-metal (MIM) configuration over a wide temperature (300-500 K) and frequency (100 Hz to 1 MHz) range.