The present disclosure provides a method that includes providing an integrated circuit (IC) substrate having various devices and an interconnection structure that couples the devices to an integrated circuit; forming a first passivation layer on the IC substrate; forming a redistribution layer on the first passivation layer, the redistribution layer being electrically connected to the interconnection structure; forming a second passivation layer on the redistribution layer and the first passivation layer; forming a polyimide layer on the second passivation layer; patterning the polyimide layer, resulting in a polyimide opening in the polyimide layer; and etching the second passivation layer through the polyimide opening using the polyimide layer as an etch mask.