Ultra fine pitch hybridization of large imaging detectors

Abstract

LETI has always played a major role in the development of Mercury Cadmium, Telluride (CMT) detectors, and in the flip-chip technology that goes with the packaging of such infrared arrays. Today with the increasing demand for better spatial resolution we observe the emergence of very large arrays detectors with a very fine pitch. However, the hybridization of such fine pitch detectors onto a readout circuit may be very challenging and represents one of the major limiting factors for the development of these detectors. At LETI we have developed a wafer scale flip chip technology to perform large Infrared Focal Plane Arrays (IRFPA) up to 1024 /spl times/ 1024 pixels with pitches down to 15 /spl mu/m. In this paper we describe this hybridization technique which includes bonding, underfilling and polishing steps. The detectors are interconnected to a CMOS readout circuit using very uniform Indium bumps, then all hybridized onto a wafer in one step using a collective method. With our expertise we achieve very high interconnection efficiency, good functionality and a low cost package. We are also presenting reliability results and the optical IR performance of the detectors to further prove the effectiveness of this flip-chip technology. With the emergence of new packaging challenges regarding size, material, and performance this technology may be used for other applications.