Theory of thermally stimulated charges in metal-oxide-semiconductor gate oxide

The theory of thermally stimulated charges (TSQs) due to thermal emission of trapped carriers in thin oxide film is analyzed in detail which relates TSQs to the gate voltage shifts of a metal-oxide-semiconductor transistor during an arbitrary temperature ramp. Solutions are obtained for stepped and continuous temperature ramps with a constant rate. The Simmons-Taylor formula for extracting the density of states of oxide traps is shown to be off by a numerical factor. The Lu-Sah formula used in their TSQ experiments is shown to agree with the general result of Miller-Fleetwood-McWhorter. The present TSQ theory gives a minimum full width at half maximum of 0.11 eV for the trap reported by Lu and Sah at E-V + 1.44 eV in thin silicon oxide films compared with their experimental 0.07 eV. The difference could be attributed to multiphonon absorption during thermal emission of the trapped oxide holes. (C) 1998 American Institute of Physics. [S0021-8979(98)04402-8].