CMOS image sensor wafer-level packaging

This article presents the advances in wafer-level processing and integration techniques for CMOS image sensor module manufacturing. CMOS image sensors gave birth to the low-cost, high-volume camera phone market and are being adopted for various high-end applications. The backside illumination technique has significant advantages over the front-side illumination due to separation of the optical path from the metal interconnects. Wafer bonding plays a key role in manufacturing backside illuminated sensors. The cost-effective integration of miniaturized cameras in various handheld devices becomes realized through the introduction of CMOS image sensor modules or camera modules manufactured with wafer-level processing and integration techniques. We developed various technologies enabling wafer-level processing and integration, such as (a) wafer-to-wafer permanent bonding with oxide or polymer layers for manufacturing backside illuminated sensor wafers, (b) wafer-level lens molding and stacking based on UV imprint lithography for making wafer-level optics, (c) conformal coating of various photoresists within high aspect ratio through-silicon vias, and (d) advanced backside lithography for various metallization processes in wafer-level packaging. Those techniques pave the way to the future growth of the digital imaging industry by improving the electrical and optical aspects of devices as well as the module manufacturability.