A model for the "Fixed" charge at the Si/SiO2interface

The "fixed" electric charge at the Si/SiO2interface is a function of oxidation tube "age" and is remarkably affected by the substrate orientation and oxide quenching rate. Low temperature annealing affects this charge. A model to explain these phenomena is offered implying that defect centers in the oxide film are responsible for the fixed charges and also for instabilities found in MOS devices. An AI atom can form a center which acts as a hole trap and would be responsible for the "negative" instabilities found in these devices and reported in the recent literature.