In-situ integrated oxide etch process particularly useful for copper dual damascene

Abstract

An integrated in situ oxide etch process particularly useful for a counterbore dual-damascene structure over copper having in one inter-layer dielectric level a lower nitride stop layer, a lower oxide dielectric, a lower nitride stop layer, an upper oxide dielectric layer, and an anti-reflective coating (ARC). The process is divided into a counterbore etch and a trench etch with photolithography for each, and each step is preferably performed in a high-density plasma reactor having an inductively coupled plasma source primarily generating the plasma and a capacitively coupled pedestal supporting the wafer and producing the bias power. The counterbore etch preferably includes at least four substeps of opening the ARC, etching through the upper oxide and nitride layers, selectively etching the lower oxide layer but stopping on the lower nitride layer, and a post-etch treatment for removing residue. The trench etch preferably includes the five substeps of opening the ARC, etching through the upper oxide layer but stopping on the upper nitride layers, a first post-etch treatment for removing residue, a nitride removal of the exposed portions of the upper and lower nitride layers, and a second post-etch treatment for remaining further residues. The oxide etches selective to nitride are accomplished using a fluorocarbon chemistry with high bias and a high temperature for a silicon-based scavenger for fluorine placed next to the plasma. The nitride etches and removal are accomplished by adding an oxygen-containing gas to a fluorocarbon. The final nitride removal is accomplished with very low bias power to increase selectivity to nitride and reduce sputtering of the underlying copper. The post-etch treatments are oxygen plasmas with zero bias power.