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Copper bumping for fine pitch interconnections |
Ziyu LIU1,Jian CAI1,2( ),Qian WANG1,Xiyun CHENG1,Lulu SHI1 |
1. Institute of Microelectronics, Tsinghua University, Beijing, 100084, China
2. Tsinghua National Laboratory for Information Science and Technology, Beijing, 100084, China |
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Abstract Fine pitch copper bumping on wafers was characterized to meet the demand for smaller interconnections. Electroplating copper bumping involves under bump metallization (UBM) sputtering, thick photoresist, copper electroplating, photoresist removal and UBM etching. The spin coating, soft baking, exposure, developing and post exposure baking of AZ4620 thick photoresist were optimized theoretically. Wet and dry UBM etching are also compared. Copper bumps were fabricated with a 20 μm pitch, 10 μm diameter and 10 μm height with a 83.95° sidewall. The wafer level copper strength uniformity was also checked by shear testing.
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| Keywords
thick photoresist
copper bumping
fine pitch interconnection
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Issue Date: 15 January 2014
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2014,
Vol. 54
