Stress corrosion induced voiding of patterned metal layers is avoided or substantially reduced by removing etching residues before gap filling. Embodiments include etching an Al or Al alloy layer employing fluorine and/or chlorine chemistry, wet cleaning, treating with a plasma containing ammonia or ammonia and oxygen at a temperature of at least about 400° C. and gap filling with a dielectric material, e.g. HDP oxide by HDP CVD.