Caroline S Lee

US Patent:

54922356, Feb 20, 1996

Filed:

Dec 1, 1994

Appl. No.:

8/347873

Inventors:

Douglas E. Crafts - San Jose CA
Venkatesan Murali - San Jose CA
Caroline S. Lee - Fresh Meadows NY

Assignee:

Intel Corporation - Santa Clara CA

International Classification:

H01L 2192

US Classification:

216 13

Abstract:

A method for removing Ball Limiting Metallurgy (BLM) layers from the surface of a wafer in the presence of Pb/Sn solder bumps. In one embodiment, the BLM comprises two layers: titanium and copper. After Pb/Sn solder bumps have been formed over the electrical contact pads of the wafer, the BLM copper layer is etched with a H. sub. 2 SO. sub. 4 +H. sub. 2 O. sub. 2 +H. sub. 2 O solution. While removing the copper layer, the H. sub. 2 SO. sub. 4 +H. sub. 2 O. sub. 2 +H. sub. 2 O etchant also reacts with the Pb/Sn solder bumps to form a thin PbO protective layer over the surface of the bumps. When the copper layer has been etched away, the titanium layer is etched with a CH. sub. 3 COOH+NH. sub. 4 F+H. sub. 2 O solution. The PbO layer formed over the surface of the Pb/Sn solder bumps remain insoluble when exposed to the CH. sub. 3 COOH+NH. sub. 4 F+H. sub.