Small Pitch Flip-Chip Interconnects for Focal Plan Arrays/Readout Integrated Circuit Hybridization

Infrared night vision is a key technology employed by the U.S. military for multiple critical applications. The cameras utilize detector pixel arrays (often composed of HgCdTe) hybridized to silicon read out circuitry. For next generation applications, the goal is to reduce pixel pitch and increase the number of pixels in the chip to improve image resolution and increase the instantaneous area that may be imaged. While indium bump to indium bump hybridization has been successfully employed to date, it becomes increasingly difficult to fabricate the interconnects as the pitch decreases. The new hybridization approach proposed herein will achieve smaller pitch when compared to the current state of the art. The proposed EPIR approach addresses the key limiters in the current technology through improved management of the lateral spread of the mated indium bumps during hybridization, while still accommodating the non-planarity and non-parallelism between the parts to be hybridized. Existing processing methods which are capable of smaller pitch will be employed, without the need for major development effort; the functionality of the structure to make good electrical contact over large areas is maintained while the inherent pitch capability is improved.