Patent ID: 8299611

Claim:
A structure fabrication method, comprising: providing a structure which includes a first dielectric layer which includes a top dielectric surface, an electrically conductive line in the first dielectric layer, a second dielectric layer on the first dielectric layer and the electrically conductive line, and a patterned polyimide layer on the second dielectric layer; forming a ball-limiting-metallurgy (BLM) region on the second dielectric layer, the electrically conductive line, and the patterned polyimide layer, wherein the BLM region is electrically connected to the electrically conductive line; and forming a solder ball on the BLM region, wherein the solder ball is electrically connected to the BLM region, wherein the BLM region has a characteristic that a length of the longest straight line segment which is parallel to the top dielectric surface of the first dielectric layer and is entirely in the BLM region does not exceed a pre-specified maximum value, and wherein the pre-specified maximum value is at most one-half of a maximum horizontal dimension of the BLM region measured in a horizontal direction parallel to the top dielectric surface of the first dielectric layer.