Copper bumping for fine pitch interconnections

Ziyu LIU; Jian CAI; Qian WANG; Xiyun CHENG; Lulu SHI

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Journal of Tsinghua University(Science and Technology) ›› 2014, Vol. 54 ›› Issue (1) : 78-83.

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Copper bumping for fine pitch interconnections

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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.

Key words

thick photoresist / copper bumping / fine pitch interconnection

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Ziyu LIU, Jian CAI, Qian WANG, Xiyun CHENG, Lulu SHI. Copper bumping for fine pitch interconnections[J]. Journal of Tsinghua University(Science and Technology). 2014, 54(1): 78-83

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