Back Illuminated CMOS Detector Arrays

The low-cost, high-yield CMOS technology developed for digital memory fabrication is finding application in making low cost image sensor arrays. The CMOS arrays also have superior radiation hardness compared to CCD image sensors due to the fundamental differences in their readout. One major limitation of CMOS imaging arrays for military and scientific applications is the reduction in net quantum efficiency due to the fraction of the pixel taken up by the readout circuits within each pixel. In addition, the spectral response of the front side illuminated CMOS array is limited compared to backside illuminated CCD's whose spectral response extends into the ultraviolet and the near infrared and provide 100% optical fill factor. Developing the capability to manufacture back-illuminated versions of CMOS arrays can improve system performance and reduce production costs for a wide range of military and commercial sensors. The overall program goal is to develop back illuminated CMOS arrays for use in a representative military image sensor, evaluating the performance of these arrays for such applications, and to build instruments around these improved low cost image sensors for military applications.BENEFITS: CMOS focal plane arrays (FPAs) are much less costly than industry standard CCD FPA, and the production costs of back illuminated CMOS FPAs could be correspondingly less expensive than high performance back illuminated CCDs. The envisaged lowered cost would open up commercial markets to systems such as UV spectrometers and hyper-spectral imagers that were formerly only affordable for military applications. The private-sector application of these back illuminated CMOS arrays would parallel those military applications where low power, low cost, and compact size are of value. This would include inspection of nuclear reactors/power plants, endoscopy, satellite-based star trackers, and night vision.