Charge Phenomena in dc Reactively Sputtered SiO2 Films

Abstract

The charge behavior of dc reactively sputtered SiO₂ films has been studied. We observed insulator charge of both polarities in the SiO₂–Si structure, depending on the sputtering conditions. When the SiO₂ layer is deposited under high‐cathode‐voltage low‐gas‐pressure conditions, the insulator charge is positive; when the SiO₂ layer is deposited under low‐cathode‐voltage high‐gas‐pressure conditions, the insulator charge is negative. This, we propose, is attributed to the adsorption of oxygen ions, which are generated in oxygen glow discharges, on the silicon surface, and the deposited SiO₂ layer during the oxide deposition. Published work on ion yield under varying plasma conditions can be cited to support this model. These ions appear to exist throughout the bulk of the oxide, but are predominantly found at or near the SiO₂–Si interface. After annealing at 800°C in dry oxygen, only ions at or near the interface are observed. Results of bias and temperature stresses on the films deposited under different conditions are also described.