Ball-limiting-metallurgy layers in solder ball structures

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 polyimide layer on the second dielectric layer;
• specifying a maximum horizontal dimension for a ball-limiting-metallurgy (BLM) region measured in a horizontal direction parallel to the top dielectric surface of the first dielectric layer,
• after said specifying is performed, determining a maximum length which is equal to one half of the specified maximum horizontal dimension;
• after said determining is performed, designing a pattern to be transferred to the polyimide layer such that the subsequently formed BLM region formed on the polyimide layer 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 the determined maximum length;
• after said designing is performed, transferring the pattern to the polyimide layer;
• after said transferring the pattern to the polyimide layer is performed, forming the BLM region on the second dielectric layer and the electrically conductive line, 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, and wherein the BLM region has said characteristic.