Spectroscopic investigation of oxide states responsible for hot-carrier degradation

Abstract
Hole‐trap states in the gate oxide of a Si metal‐oxide‐semiconductor field‐effect transistor (MOSFET) are investigated by inhomogeneous excimer laser irradiation. Subbandgap ultraviolet light photons with an energy exceeding a threshold lying between 5.5 and 6.4 eV were found to excite electrons from these originally neutral states into the SiO2 conduction band. A fixed positive charge is left behind. The degradation in MOSFET performance due to the irradiation is comparable to that accompanying hot‐hole injection. Also, subsequent hot‐electron stress changes the device characteristics in a way similar to hot‐electron stress following hot‐hole stress. It is concluded that the traps responsible for hot‐carrier degradation cause the optically induced charge trapping.