CMOS Image Sensors

An image sensor is a device that converts a visual image to an electric signal, which is used mostly in digital cameras and other imaging devices. It is a set of charge-coupled device (CCD) or active-pixel sensors (APS) like CMOS sensors. The pixel responds to the light by accumulating charges - the more light, the more charge. Thereby the optical signal is transformed into an electric signal, which gets converted into digial information. Compared to CCD, CMOS sensors are faster, smaller, and cheaper as they are more integrated, which makes them also more power efficient.

Originally image sensors were assembled in ceramic packages with glass cover and wire bonding. The key motivation of wafer-level chip-scale-packaging (WL-CSP) is to improve assembly yield, reduce manufacturing cost, and realize a smaller form factor. WL-CSP technology is a mixture of front-end technologies (photolithography, etching, sputtering, silicon-to-glass bonding, etc.) and back-end technologies (via hole laser drill, electroplating, redistribution, solder bumping, etc.). Electrical connection from image sensor pad to Si backside bump is one of the key techniques, where TSV is becoming the industry standard.

Based on well established double side mask alignment systems, EV Group offers a product portfolio which covers all essential process steps for the back-end lithography, such as wafer bumping, creation of redistribution layer (RDL) and via etching masks, via bottom opening processes as well as lithography performed on thin or temporary bonded wafers. Such wafers may be aligned based on alignment keys on a wafer backside or placed in the (temporary) bond interface, where mask aligners with backside microscopes, transmissive or reflective infrared alignment capability are applied. Such systems can be configured in semi-automated configurations for process development and manufacturing as well as fully-automated system configurations running cassette-to-cassette processes for high-volume manufacturing.

Please see our related products EVG®620, EVG®6200, IQ Aligner® and EVG®40NT for detailed information.


Tessera's latest MVP packaging. Courtesy of Tessera.