Interface State Density Reduction and Effect of Oxidation Temperature on Fluorine Incorporation and Profiling for Fluorinated Metal Oxide Semiconductor Capacitors

Abstract

The effect of fluorine incorporation on the as‐grown interface state density of the system was investigated using MOS capacitors with fluorinated oxide dielectrics grown by oxidation as test structures. A clear reduction of the interface trap density, attributed to fluorine‐induced passivation of interfacial dangling bonds, weak bonds, and weak interactions, was shown for additions in the parts‐per‐million range as compared to dry oxides. Fluorine incorporation in the oxide was investigated with SIMS profiling. The application of a pulsed oxidation process in which the fluorine source is added to the oxidant in intervals within the total oxidation time demonstrated that the variation of oxidation processing parameters strongly influences the resulting fluorine profile. A two‐peak pattern of the fluorine profile, with one peak in the interfacial area and the other corresponding to the oxide area grown during the step, was observed. This pattern was strongly dependent on the oxidation temperature, with the interfacial fluorine accumulation more pronounced with increasing temperature. The pronounced influence of the oxidation temperature on the fluorine profile resulting from oxidation was ascribed to a thermally activated replacement reaction of bonded fluorine by oxygen.