Patent Number: 7,825,511

Title: Undercut-free BLM process for Pb-free and Pb-reduced C4

Abstract: A system and method for eliminating undercut when forming a C4 solder bump for BLM (Ball Limiting Metallurgy) and improving the C4 pitch. In the process, a barrier layer metal stack is deposited above a metal pad layer. A top layer of the barrier layer metals (e.g., Cu) is patterned by CMP with a bottom conductive layer of the barrier metal stack removed by etching. The diffusion barrier and C4 solder bump may be formed by electroless plating, in one embodiment, using a maskless technique, or by an electroplating techniques using a patterned mask. This allows the pitch of the C4 solder bumps to be reduced.

Inventors: Daubenspeck; Timothy H. (Colchester, VT), Gambino; Jeffrey P. (Westford, VT), Muzzy; Christopher D. (Burlington, VT), Sauter; Wolfgang (Richmond, VT)

Assignee: International Business Machines Corporation

International Classification: H01L 23/12 (20060101)

Expiration Date: 2019-11-02 0:00:00