Resist protection of ball limiting metal during etch process

Details Resist protection of ball limiting metal during etch process Resist protection of ball limiting metal during etch process

1993-12-10

1995-01-24

Chaudhuri, Olik

Fishing, trapping, and vermin destroying

156664, 156666, H01L 2144, H01L 2148

Patent

active

053842839

ABSTRACT:
A method of making integrated circuit chip to substrate connections first deposits a blanket layer of CrCu over a completed wafer which has terminal vias etched in the final insulator. Then PbSn solder is electrolytically plated through a photoresist mask. After the plating is done, the resist is removed and the Cu is etched using the solder dot as a mask, and then the solder dots are melted to form spheroid or ball shapes. Next, a positive photoresist is applied in a manner that distributes the photoresist around the base of the solder balls. The solder balls are then used as a self-aligned exposure mask. Since the photoresist under the balls is not exposed, each ball has a concentric layer of resist at the base after exposure and development. This concentric layer of resist protects the Cu/PbSn interface and is used as the mask for etching excess Cr. The resist is then removed.

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