Hot-Electron-induced MOSFET Degradation—Model, Monitor, and Improvement

Evidence suggests that MOSFET degradation is due to interface-states generation by electrons having 3.7 eV and higher energies. This critical energy and the observed time dependence is explained with a physical model involving the breaking of the = Sis H bonds. The device lifetime is proportional to I-2sub 9 I1d9ΔV15t. If Isubis large because of small L or large Vd, etc., τ will be small. Isub (and possibly light emission) is thus a powerful predictor of τ. The proportionality constant has been found to vary by a factor of 100 for different technologies, offering hope for substantially better reliability through future improvements in dielectric /interface technologies. A simple physical model can relate the channel field Em to all the device parameters and bias voltages. Its use in interpreting and guiding hot-electron scaling are described. LDD structures can reduce Em and Isub and, when properly designed, reduce device degradation.