Photon Energy Dependence of Radiation Effects in MOS Structures

Abstract

MOS capacitors with oxide thicknesses of 750R, 3500A and 6000R were irradiated using a Co60 source and a Cu target x-ray tube. At low fields across the oxides (<lMV/cm), shifts in the flatband voltages observed with Co60 were twice those measured with the Cu tube at the same oxide dose. At higher fields (>lMV/cm) the differences disappear. The observations are interpreted to be due to differences in the electron-hole recombination dynamics for the two radiation energies. Additionally, it was observed that the SiSiO2 interface states trap holes with an efficiency that decreases as the square root of the electric field across the oxide.

Field Dependence of Charge Yield in Silicon Dioxide

“…Yield for thick oxides (the original data was from the 1980 paper [5]) were up to an order of magnitude lower than the line that they fitted to their overall data set. Those low data points were taken at room temperature.…”

“…Dozier and Brown measured charge yield on capacitors with several different oxide thicknesses in 1980 [5]. Their measurements were done at room temperature, where significant charge transport takes place.…”

“…11, after [5], which shows room-temperature data on capacitor test structures where charge yield was adjusted with a field-dependent factor to account for hole capture during transport. The authors used a field dependence of .…”

“…At low fields, correction factors of more than a factor of 10 are required to account for this effect, which does not occur in low-temperature experiments where holes are frozen in place. The interpretation of charge yield from measurements at temperatures and fields where holes undergo transport, such as the Dozier-Brown study [5], depends on the applicability of such large correction factors. 3 Bulk recombination corrections may also depend on oxide thickness.…”

X-ray radiation effects in multilayer epitaxial graphene

“…In this study, we focus on the effects of X-rays, which are typically not energetic enough to cause direct lattice damage, but may create other long-term defects such as charge traps [5].…”