Experimental determination of the frequency factor of thermal annealing processes in metal–oxide–semiconductor gate-oxide structures

Radiation-induced trapped charge annealing processes in the gate and field oxides of metal–oxide–semiconductor field-effect transistors are thermally activated. The activation energy and the frequency factor are related to the relaxation time constant by an Arrhenius law. A simple measurement of the relaxation time constant defines the activation energy, frequency factor (E,ν) pair. Choosing arbitrarily a “realistic” frequency factor corresponds to determining a characteristic energy, on which depends any subsequent annealing prediction. A controversy exists about the appropriate value of ν for silicon dioxide, with published values ranging from 1×107 to 1×1014 s−1. In this paper, a new method is presented that yields values for both frequency factor and activation energy. This method leads to an unexpectedly low (but consistent) value of ν (about 1×107 s−1) when applied to three different devices, obtained from three different manufacturers. The experimental procedure and the results for all three cases are presented and discussed.