Novel Fabrication and Packaging Technologies using Wafer Level Cameras
The increasing demand for more functions and features coming along with cost reduction plays a significant role in today’s product design and manufacturing technologies of mobile devices such as PDAs, laptop computer and mobile phones. Besides the main function of the device, imaging is considered as core feature by the user and major mobile phone manufacturers. Therefore the industry puts a lot of effort onto performance improvements and the optimization of the manufacturing method of mobile phone cameras. Wafer Level Camera (WLC) is supposed to be the technology of choice to address these requirements. In recent years Wafer Level Packaging of CMOS image sensors has become a well established technology in the industry. This technology provides a cost efficient packaging method for shrinking devices sizes coupled with higher I/O density. In addition to this Wafer-level optics is a novel technology that is designed to meet the demand for smaller form factors of the optical system and cost reduction in the next generation of camera phones. The optical components are fabricated by replicating the optics through a stamp material into a polymer layer, coated on a glass wafer. Another key challenge is the wafer alignment. Replicated lens wafers are aligned and adhesively bonded at the wafer level using a UV curing process in order to achieve excellent alignment results. Finally the bonded Opto Wafers are subsequently diced to form individual camera modules [1]. Also wafer level packaging of the CMOS wafer using bonding techniques is part of this paper. UV curable materials for microlens replication and for Wafer Level Packaging of Opto Wafers (lens stacking) is presented as well. Optical measurement technology for quality assurance of micro-lenses finally concludes the paper.
