Dependence on gate work function of oxide charging, defect generation, and hole currents in metal-oxide-semiconductor structures

Abstract

Oxide charge trapping and current sensing techniques are used to test for enhanced anode hole generation from metal-oxide-semiconductor devices with gate electrodes of increasing work function during hot electron stress. In this study, the gate work function variation was obtained by comparing devices with polycrystalline silicon gates doped degenerately with either phosphorus or boron. Contrary to expectation, significant differences were not observed in hole currents carried in the silicon substrate valence band of these devices. However, differences were seen in oxide charging, interface-state formation, and neutral trap generation. The enhanced positive charging observed on devices with larger work function boron-doped gates is discussed in terms of mechanisms related to slow donorlike state formation caused by hydrogen release and reaction at energies of less than 5 eV. © 1997 American Institute of Physics.