Introduction
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.
