Oxide thickness dependence of interface trap generation in a metal-oxide-semiconductor structure during substrate hot-hole injection

Abstract

Oxide thickness dependence of interface trap generation in a metal-oxide-semiconductor (MOS) structure is investigated using uniform hot-hole injection into the gate oxides of p-channel MOS transistors with very thin oxide thicknesses. Significant dependence of interface trap generation on oxide thickness (tox) is found for very thin oxides and the dependence disappears for tox≥8 nm. A universal relationship between hole trapping in the oxide bulk and interface trap generation at the Si/SiO2 interface is observed experimentally. The experimental results suggest that interface trap generation is a process involving hole trapping in the oxide bulk, rather than a pure interfacial process. No oxide thickness dependence of interface trap generation for thicker oxides (tox≥8 nm) is in agreement with previous reports and the overall dependence can consistently be explained with the help of the spatial distribution of trapped holes in the oxide. In contrast to the reports describing delayed interface trap formation, we observed oxide field-dependent annealing of the generated interface traps after the end of hole injection.