Study of rf-sputtered yttrium oxide films on silicon by capacitance measurements

Yttrium oxide Y2O3 films are prepared by rf sputtering on to silicon substrates and characterized by current-voltage I-V, capacitance-voltage C-V and capacitance-time C-t measurements. Relative permittivity increases with substrate heating from room temperature to 600 °C. As-deposited films show large flat-band voltage and interface trap density, which improve upon annealing in oxygen or hydrogen ambient up to 600 °C. However, film resistivity degrades by about 1 order of magnitude. Large hysteresis is observed in the C-V curves, particularly for films deposited at high substrate temperature. This observation is attributed to the interfacial polarization at the Y2O3/SiO2 (native) interface. By monitoring the device capacitance over time for a given applied voltage, the resultant curves can be fitted to an exponential time dependent relation: C(t)=α0−α1exp(−t/τ). The time constant is further found to exhibit a dependence on the applied voltage of the form τ=τ0exp(−V0/V). Comparison with electron-beam deposited films is also made.