Stress induced degradation and reliability of Al2O3 thin film on silicon

The electrical properties of metal insulator semiconductor (MIS) devices with Al2O3 as dielectric layer deposited by reactive RF (radio frequency) magnetron sputtering were investigated using Capacitance-Voltage (C-V) and Current-Voltage (I-V) to determine the quality of oxide layer and oxide/silicon interface. To assess the reliability of Al2O3/Si interface constant current stress of 1 mA for varying time period was also investigated. The effect of post deposition annealing (PDA) on electrical behavior of Al/Al2O3/Si MOS (metal oxide semiconductor) capacitors was studied. Annealed devices show substantial improvement in interface trap charge density (Dit), fixed oxide charge density (Qf) and leakage current. Improved electrical and interface properties are achieved at annealing temperature of 425 °C. Incorporation of nitrogen gas improves the thermal stability of Al2O3 films which exhibited fewer shift in flat band voltage (Vfb) as compared to the samples grown in pure argon atmosphere. Breakdown voltage for nitrogen doped Al2O3 of 30 nm thin films was enhanced from 15 V to 19 V. Results indicate that reactive sputtering in N2 containing plasma is a promising approach as reduction in gate leakage current and power dissipation is utmost essential for integrating high-k material into semiconductor processing.