METHOD FOR FORMING BUMPS ON UNDER BUMP METALLURGY

摘要

A method for forming metal bumps is provided. A bonding pad is first formed on the active surface of a chip and then a passivation layer is formed on the active surface of the chip and exposes the bonding pad. An under bump metallurgy is formed on the active surface of the chip to overlay the bonding pad. A layer of patterned photoresist is formed on the under bump metallurgy and exposes the portion of the under bump metallurgy on the bonding pad. A layer of copper is plated on the exposed portion of the under bump metallurgy and then a layer of solder is printed on the copper layer. Afterward the solder is reflowed to form a spherical metal bump. Finally, the photoresist layer is removed and the exposed portion of the under bump metallurgy is etched out.