Development of a new indium bump fabrication method for large-area HgCdTe detector

Indium bumps are widely employed in high density interconnection between infrared focal plane arrays and Si read out integrated circuits by flip-chip bonding. Indium bump array formation is a critical step in the flip-chip fabrication process. Taller and higher uniformity indium bumps are necessary for high pixel density and low noise photodetectors. In this work, a new process of indium bumping through evaporation and ion etching was developed to produce ultrafine pitch indium bumps for assembly of large-area HgCdTe photodetector. Electron microscopy was used to analyze and evaluate the microstructure, height and uniformity of indium bumps. The results showed 7 μm height indium bumps with 10 μm pitch were easily achieved. The bump height and uniformity were significantly improved with our new developed indium bump fabrication method.