We develop novel micro-bumping technology to realize small size, fine pitch and uniform height Cu/Sn bumps. Electroplated-evaporation bumping (EEB) technology, which is a combination of Cu electroplating and Sn evaporation, is developed to achieve uniform height of Cu/Sn bumps. We develop CMOS compatible dry etching processes for removing sputtered Cu/Ta layers to achieve small size and fine pitch Cu/Sn bump. 5 µm square and 10 µm pitch Cu/Sn micro-bumps are successfully fabricated for the first time. Bump height variation is 5 µm ±3 % (95%, 2σ), which is uniform compared to electroplated Cu/Sn bumps. We evaluate micro-joining characteristics of Cu/Sn micro-bumps. Good I–V characteristics are measured from the daisy chain consisting of 1500 bumps with 10 µm square and 20 µm pitch. Resistance of Cu/Sn bump is 35 mΩ/bump, which is very low value compared to electroplated Cu/Sn bumps.
['Yuki Ohara', 'A. Noriki', 'Katsuyuki Sakuma', 'Kang Wook Lee', 'M. Murugesan', 'Jichoel Bea', 'Fumiaki Yamada', 'Takafumi Fukushima', 'Tetsu Tanaka', 'Mitsumasa Koyanagi']
10 µm fine pitch Cu/Sn micro-bumps for 3-D super-chip stack