Frequency dependence of accumulation capacitance of MOS structure with ultrathin oxide layer

Ultrathin oxide (2-20 nm) of silicon is grown on (100) oriented n-Si, by wet oxidation at a reduced water vapour pressure (0.04 atm.). The thin oxide layer is characterized by preparing Al/thin SiO2/n-Si MOS capacitors. The capacitance-voltage (C-V) and the conductance-voltage (G-V) characteristics are measured at 10 kHz and 1 MHz frequencies. The accumulation capacitance is observed to be dependent on frequency and this dependence increases with the decrease in the oxide thickness. The series resistance associated with the device structure is estimated. The resistance slate density (Dit) and fixed oxide charge density (Qf) are estimated from the G-V and C-V characteristics respectively.