US Patent 7300864 Method for forming solder bump structure

A solder bump structure may be formed using a dual exposure technique of a photoresist, which may be a positive photoresist. The positive photoresist may be coated on an IC chip. First openings may be formed at first exposed regions of the photoresist by a first exposure process. Metal projections may be formed in the first openings. A second opening may be formed at a second exposed region of the photoresist by a second exposure process. The second exposed region may include non-exposed regions defined by the first exposure process. A solder material may fill the second opening and may be reflowed to form a solder bump. The metal projections may be embedded within the solder bump.