Theory of channel hot-carrier degradation in MOSFETs

A critical but still poorly understood process in metal-oxide-semiconductor field-effect transistors (MOSFETs) is stress-induced changes in device threshold voltage, channel conductance, etc. which limit the operating lifetimes of the transistors. However, the degradation characteristics of deep-submicron MOSFETs, the widely demonstrated deuterium/hydrogen isotope effect, and the related results of scanning-tunneling microscopy-based depassivation experiments on silicon-vacuum interfaces are providing new insights into the degradation of MOSFETs via, at least, depassivation of the silicon-oxide interface. In this manuscript, we review the basic mechanisms of depassivation, suggest disorder-induced variations in the threshold energies for silicon-hydrogen/deuterium bond breaking as a possible explanation for observed sublinear time dependencies for degradation below t^0.5, and show that excitation of the vibrational modes of the bonds could play a significant role in the continuing degradation of deep-submicron MOSFETs operated at low voltages.