Bumping process and structure thereof

摘要

A bumping process is provided as following: at first, providing a wafer, then forming a first photo-resist layer on a active surface of the wafer and forming at least a first opening on the first photo-resist layer; and forming a first copper pillar in the first opening; then forming a second photo-resist layer on the first photo-resist layer and forming at least a second opening on the second photo-resist layer, wherein the second opening is bigger than the first opening so that the first copper pillar and the surrounding first photo-resist layer are exposed in the second opening; and forming a second copper pillar in the second opening; finally forming a solder layer onto the second pillar, and removing the first and second photo-resist layers.