Method of forming an isolation trench in a semiconductor substrate

摘要

A method of defining in a substrate of silicon an active region, a region of field oxide and an isolating wall of silicon dioxide therebetween in a single masking step. The substrate is covered in succession with a thin layer of silicon dioxide, a thick layer of silicon nitride and a first film of titanium. The first film of titanium is covered with a layer of photoresist which has a removed portion and a retained portion in registry with the active region. The first film of titanium and the layer of silicon nitride are etched through the removed portions of the layer of photoresist to form an opening extending to the thin layer of silicon dioxide and partially underlying the retained portion of the photoresist layer by a predetermined lateral distance. A second film of titanium is deposited on the retained portion of the photoresist layer and the exposed portion of the thin layer of silicon dioxide. The retained portion of the photoresist layer with the portion of the second film of titanium thereon is removed. Thus, an edge of the retained portion of said first film of titanium is laterally spaced from an adjacent edge of the retained portion of the second film of titanium deposited on the thin layer of silicon dioxide by approximately the aforementioned predetermined lateral distance. Using the first and second thin layers of titanium, a trench is etched into the substrate. The trench is thereafter filled with silicon dioxide.