Method of depositing thin films of small dimensions utilizing silicon

Abstract

A method for depositing thin film patterns of very small and controllable dimensions in the fabrication of integrated circuits which avoids edge tearing of the films. A non-photosensitive organic polymeric first masking layer is deposited on the integrated circuit substrate. Upon this layer is deposited a layer of silicon nitride using plasma deposition techniques employing a gaseous source. The silicon nitride layer is covered by a second masking layer, preferably an organic polymeric resist material, through which apertures are formed in preselected patterns using standard lithographic masking and etching techniques. The silicon nitride layer is then reactive ion etched with CF.sub.4 through the apertures formed in the second masking layer. The first masking layer is then etched through the apertures in the second masking layer and silicon nitride layer using reactive ion etching techniques. The etching of the first masking layer continues until the first masking layer is undercut beyond the edges of the aperture in the silicon nitride layer so that the silicon nitride layer forms an overhang of the aperture in the first masking layer. The thin film to be deposited is then applied over the resulting structure including the surface of the silicon nitride layer and the substrate exposed through the apertures. Because of the overhang, a discontinuity is formed between the thin film deposited upon the exposed surface of the substrate and that formed upon the outer surface of the silicon nitride layer so that when the first masking layer is dissolved, the film deposited upon the substrate is left without any edge tearing between it and the removed portions of the film.