A Fine Pitch And High Aspect Ratio Bump Array For Flip-chip Interconnection

This paper describes a bump-fabrication process for a fine pitch and high aspect ratio bump array. The fabricated bumps had a 10 pm pitch with a 5 Dm diameter and a 20 D m height, and were arranged 5 pm apart from each other. The bumps were made of a copper base pillar and a solder cap, and were located on the device circuit area to realize high reliability flip-chip interconnections. A microstructual resist patterning technique to form a fine pitch and high aspect ratio bump array has been developed. The characteristics of the positive type photoresist were investigated to explicate the fundamental behaviors by evaluating the alkaline solubility and the dissolution effect. Also, the factors which affect the resist patterning accuracy were also elucidated to obtain precise resist pattern.