Impedance of defective silicon layers formed in Al/SiO2/n-Si structures by irradiation with high-energy helium ions

Abstract

Al/SiO2/n-Si MOS structures irradiated with 5 MeV helium ion are studied. The irradiation fluence varied from 10^10 to 10^12 cm^−2. The capacitance–voltage (C-V) characteristics, frequency dependences of impedance Z and DLTS spectra were measured. It was found that irradiation leads to an increase in Z' of structures in the depletion mode in the frequency range f = 2–500 kHz. Compensation of doping impurity by radiation-induced defects is accompanied by a decrease in the capacitance of structures in the deep inversion mode. DLTS spectroscopy confirmed that the surface states density increase, caused by helium ion irradiation, affects impedance spectra of the structures.