A method for forming a high-quality aluminum-copper alloy pattern over a semiconductor substrate. The method first forms an aluminum-copper alloy layer over a semiconductor substrate, and then performs a rapid thermal processing operation to remelt copper extracts into the alloy bulk. Subsequently, a photoresist layer is formed over the alloy layer. Finally, the alloy layer is etched to transfer the pattern from the photoresist layer to the metallic alloy layer. Unlike a conventional method that can lead to abnormal conduction due to the presence of extracts that are difficult to etch, this invention uses a thermal operation to remove the extracts before etching is conducted. Hence, the masking effect due to etching is mostly prevented.

A new method of metal deposition with reduced metal residue after metal etching by cooling the wafer before metal deposition is described. A first patterned conducting layer is provided overlying a dielectric layer on the surface of a semiconductor substrate. The wafer is cooled to a temperature of less than about 20.degree. C. Thereafter, a metal layer is deposited overlying the first patterned conducting layer. The metal layer is etched away where it is not covered by a mask to complete formation of the metal line. Cooling of the wafer before metal deposition decreases the metal residue found after metal etching.