SEALING SILICON-NITRIDE REMOVAL IN SILO FIELD ISOLATION FOR SUBMICRON TECHNOLOGIES

Silicon nitride can be oxidized by a Caro's solution (mixture of sulfuric acid and oxygen peroxide) at low temperatures (around 170-degrees-C). Optical (ellipsometry) and physical (Auger, x-ray photoelectron spectroscopy) characterization of the oxidized thin films shows that the cold oxidation mechanism is a diffusion-type mechanism rather than a surface reaction mechanism. This property is used to remove the sealing nitride layer of a sealed interface local oxidation (SILO)/rapid thermal nitridation field isolation process, applied to high-density submicron CMOS device manufacturing. In this scheme, the sealing nitride removal is one of the most critical steps to achieve high-quality gate oxide. This process is preferred as a noncontaminating alternative to other possible processes, in terms of surface contamination or gate oxide defectivity.