The effect of substrate resistivity on threshold voltage shifts due to radiation-induced damage in IGFET

The authors describe the dependence of the radiation-induced threshold voltage shift (ΔV_t) of n-channel IGFET devices on the substrate doping concentration and the concentration of segregated boron atoms in the oxide. Substrate resistivities of 0.1 and 0.5 ohm/cm were used. The thicknesses of the investigated gate oxides varied from 17.0 to 50.0 um. The devices were irradiated with Al K_α (1.49 keV) X-rays to different radiation doses at identical dose rates. The threshold voltages were measured before and after irradiation, employing an optically assisted hot electron injection technique. Following irradiation and hot electron injection, the threshold voltage shifts due to fixed positive charge (ΔV_FPC) and neutral electron traps (ΔV_NET) were determined. The radiation-induced threshold voltage shifts due to FPCs were greater for the 0.5 ohm/cm wafer than for the 0.1 ohm/cm wafer, and the threshold voltage shifts due to NETs were greater for the 0.1 ohm/cm substrate. The interface concentration of boron in the oxide at different depths obtained from Suprem-III simulations was related to induced threshold voltage shifts