Abstract: A process for defining vias through a polyimide and silicon nitride layer is disclosed. After the deposition of a first layer of silicon nitride and a second layer of polyimide, a layer of photoresist capable of producing negatively sloped walls is then lithographically defined with a pattern of vias. After the photoresist is developed, the polyimide layer is etched with a CF.sub.4 O.sub.2 gas mixture using the developed photoresist layer as etch mask. The silicon nitride layer is then etched with a CF.sub.4 /H.sub.2 gas mixture using the etched polyimide layer as an etch mask.

Abstract: In a photoresist lift-off process for depositing metal on a semiconductor substrate, a protective coating of silicon is applied to an etched via hole prior to the metal deposition step. This prevents the formation of contaminant trapping voids and contaminated chemical residues which would otherwise occur at the base of the metal line subsequently deposited in the bottom of the via hole. The protective silicon layer, which has a thickness of from 100 to 300 angstroms, remains intact as a permanent part of the structure.

Abstract: A photoresist photolithographic process is disclosed which provides for a single development step to develop a dual layer photoresist for lift-off, reactive ion etching, or ion implantation processes requiring a precise aperture size at the top of the photoresist layer.The process involves the deposition of two compositionally similar layers, with the first layer having the characteristic of being soluble in a developer after exposure to light and baking, and the second layer having the characteristic of being insoluble in the same developer after having been exposed to light and baked. With these two distinct characteristics for the two layers of photoresist, the effective aperture for windows in the composite photoresist can be tightly controlled in its cross-sectional dimension in the face of large variations in the developer concentration and development time.