Study of γ-ray irradiation influence on TiN/HfO2/Si MOS capacitor by C-V and DLTS

Abstract

Gamma-ray (γ-ray) irradiation effects on HfO2-based MOS capacitors have been studied. The capacitance-voltage (C-V) characteristic was measured at room temperature (300 K) to study the change of electrical properties in capacitors before and after irradiation with different doses. The shifts of midgap and flatband voltage and the decrease of accumulation capacitance shown that defects in the oxide and interface traps were indeed created during the gamma irradiation. Deep level transient spectroscopy (DLTS) was used to characterize the interfacial states introduced by irradiation. The activation energies, capture cross-sections and interface state densities were EC-0.1697 eV, EC-0.1929 eV; 7.371 × 10−16 cm2, 1.158 × 10−14 cm2; 1.814 × 1013 eV−1 cm2, 5.042 × 1013 eV−1 cm2 for the 1 Mrad(Si) and 5 Mrad(Si) samples, respectively. The peak shifted toward lower temperature when increasing pulse voltages (VP) in measuring DLTS spectra with fixed reverse voltage (VR). It indicated that interface defects have been formed during irradiation. With the increasing of irradiation dose, both of the capture cross section (σn) and the interface state density (Dit) increased. These results provide the basis to the researches and applications for the HfO2-based devices in the field of high-κ materials, irradiation effect, devices in radiation working environment.