Back-Illuminated Image Sensors Come to the Forefront


Swain, P. K., & Cheskis, D. (2008). Back-Illuminated Image Sensors Come to the Forefront-Novel materials and fabrication methods increase quality and lower cost of sensors for machine vision and industrial imaging. Photonics Spectra, 42(8), 46.


Demand for higher throughput inspection systems with improved resolution is growing in the machine vision and industrial imaging industries. Traditionally, front-illuminated CCD or CMOS sensors are used in these inspection systems because of the lower costs associated with their high-volume manufacturing compatibility. To keep up with the increased demand, while remaining sensitive to cost constraints, manufacturers are forced to reduce the pixel size — limiting the performance of image sensors.

To solve this problem, sensor manufacturers are turning to back illumination. Back-illuminated image sensors are becoming more commonplace in high-performance imaging systems, given the inherent benefits when compared with their front-illuminated counterparts. However, their increased manufacturing complexity and high costs have constrained them for use in higher-end systems in the machine vision, semiconductor inspection and security markets. This has limited back illumination to a select number of products that are manufactured in low volumes at a few specialty foundries.

Recently, a breakthrough in novel materials and fabrication methods was achieved that will make higher-performance back-thinned imagers readily available for mass production. Using ultrathin silicon-on-insulator wafer technology, the method will reduce the manufacturing complexity and effectively solve the cost-quality challenge.

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