Indium Surface Preparation for Improved Flip-Chip Hybridization

For IR sensors, the sensing detector and readout circuitry (ROIC) are commonly joined on a pixel by pixel level in a process referred to as Hybridization. Hybridization requires bonding an ROIC die and a detector die on a pixel level, where the total number of pixels required to bond and form interconnects ranges from 1,000,000 to 16,000,000 individual pixels. The material of choice for Hybridization is Indium, and the properties of Indium and Indium Oxide play an essential and critical role. Indium Oxide, a ceramic semiconducting material forms naturally in ambient air. This process is thermodynamically favored and occurs spontaneously; therefore all Indium material in ambient air will have a natural layer of Indium Oxide. In order to form adequate electrical contacts during Hybridization, this native Indium Oxide needs to be removed and the Indium passivated to prevent oxide growth. The subject of this proposal is to develop such a solution.