Fabrication of highly-uniform indium ball bumps for small unit-cell infrared focal plane arrays

Yingjie Ma; Xianliang Zhu; Bo Yang; Jifeng Cheng; Yi Gu; Tao Li; Xiumei Shao; Xue Li; Haimei Gong

doi:10.1117/12.2574333

5 November 2020 Fabrication of highly-uniform indium ball bumps for small unit-cell infrared focal plane arrays

Yingjie Ma, Xianliang Zhu, Bo Yang, Jifeng Cheng, Yi Gu, Tao Li, Xiumei Shao, Xue Li, Haimei Gong

Proceedings Volume 11563, AOPC 2020: Infrared Device and Infrared Technology; 1156302 (2020) https://doi.org/10.1117/12.2574333
Event: Applied Optics and Photonics China (AOPC 2020), 2020, Beijing, China

Abstract

Highly uniform ball-shaped indium bump arrays with small pixel pitches down to 10 μm have been fabricated. Multilayer stacked metal contact electrodes covered by a thin SiN_xdielectric layer serve as the under bump metallization. Indium bumps were thermally evaporated inside the SiN_x openings on top of the electrodes. Wet lift-off of the indium bumps was achieved by using a negative photoresist with precisely controlled undercuts. By comparison to a recipe without the SiN_x, the non-uniform reflow effect of the indium materials was effectively eliminated after the thermal treatment. A mean indium ball diameter of 6.05 μm with a small coefficient of variation of 2.6% was finally realized for 10 μm pitch arrays. These results demonstrate the fabrication method is promising to ensure a reliable flip-chip hybridization of ultra-fine pitch focal plane arrays to silicon readout circuits with high yield.

Citation Download Citation

Yingjie Ma, Xianliang Zhu, Bo Yang, Jifeng Cheng, Yi Gu, Tao Li, Xiumei Shao, Xue Li, and Haimei Gong "Fabrication of highly-uniform indium ball bumps for small unit-cell infrared focal plane arrays", Proc. SPIE 11563, AOPC 2020: Infrared Device and Infrared Technology, 1156302 (5 November 2020); https://doi.org/10.1117/12.2574333

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