Design and control of horizontal extension for gold bumping

Gold bump is commonly used for COG (chip on glass) packaging of LCD driver. The market of Au bump COG is growing fast. Mostly, the gold bumping is finished on the whole wafer, following the process of UBM sputtering, thick photoresist patterning, electric gold plating, etc. Gold bumps with 10/spl sim/30 /spl mu/m in height, 45/spl sim/70 /spl mu/m in pitch and 15/spl sim/25 /spl mu/m in space have been fabricated. Horizontal extension should be controlled during bumping. Design and process optimization have been done to get high quality Au bumps.