Patent ID: 6740248
Filing Date: 2004-05-25
Classification: C03C,H01L

Abstract:
A method for removing, from a semiconductor substrate, a silicon oxide gradient layer, the method comprising:providing a substrate bearing: a dielectric layer comprising a silicon oxide gradient sublayer having a maximum oxygen atom concentration at a surface thereof, the oxygen atom concentration decreasing monotonically to substantially zero with distance of material in the dielectric layer from an active surface of the substrate, the balance of the dielectric layer comprising silicon nitride; contacting the surface with an acid solution comprising phosphoric acid at a first temperature, the acid solution at the first temperature exhibiting a positive etch selectivity for silicon oxide over silicon nitride; and gradually lowering a temperature of the acid solution to a second temperature, the acid solution at the second temperature exhibiting a positive etch selectivity for silicon nitride over a material of an adjacent layer or structure.