DLTS and in situ C-V analysis of trap parameters in swift 50MeV Li 3+ ion-irradiated Ni/SiO2/Si MOS capacitors

摘要

Ni/SiO2/Si MOS structures were fabricated on n-type Si wafers and were irradiated with 50MeV Li3+ ions with fluences ranging from 1 à 1010 to 1 à 1012 ions/cm2. High frequency C-V characteristics are studied in situ to estimate the build-up of fixed and oxide charges. The nature of the charge build-up with ion fluence is analyzed. Defect levels in bulk Si and its properties such as activation energy, capture cross-section, trap concentration and carrier lifetimes are studied using deep-level transient spectroscopy. Electron traps with energies ranging from 0.069 to 0.523eV are observed in Li ion-irradiated devices. The dependence of series resistance, substrate doping and accumulation capacitance on Li ion fluence are clearly explained. The study of dielectric properties (tan δ and quality factor) confirms the degradation of the oxide layer to a greater extent due to ion irradiation. © 2011 Taylor & Francis.