Solving the poison via problem by adding n.sub.2 plasma treatment after

Abstract

A new method of forming the intermetal dielectric layer of an integrated circuit is described. A thick insulating layer is formed over semiconductor device structures in and on a semiconductor substrate. A first metal layer is deposited over the thick insulating layer. The first metal layer is etched using conventional photolithography and etching techniques to form the desired metal pattern on the surface of the thick insulating layer. The intermetal dielectric layer is formed by first covering the patterned first metal layer with a layer of silicon oxide. The silicon oxide layer is covered with a layer of spin-on-glass material which is cured. A second layer of silicon oxide completes the intermetal dielectric layer. Via openings are formed through the intermetal dielectric layer to the underlying patterned first metal layer. A vacuum bake removes moisture from the exposed spin-on-glass layer within the via opening. A nitrogen plasma treatment converts the exposed spin-on-glass layer from an organic to an inorganic material. The inorganic spin-on-glass material has less moisture absorption and suppresses outgassing from the rest of the organic spin-on-glass layer, thus preventing poisoned via metallurgy. A second metal layer is deposited overlying the intermetal dielectric layer and within the via openings and fabrication of the integrated circuit is completed.