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22 December 1989 Improved Uniformity In Thinned Scientific CCDs
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Large area image sensors using Charge-Coupled Device (CCD) technology for scientific applications are often thinned and backside illuminated to improve their overall sensitivity and particularly their short wavelength response. The usual method of fabrication is to start with a p-type (high resistivity) epi-layer on a 1)4-type (low resistivity) substrate and chemically etch the device until there is a thin membrane of the desired thickness at or near the p-p+ interface. Variations in the doping concentration at the final back surface because of nonuniform thinning often lead to poor pixel-to-pixel uniformities. Pixel-to-pixel variations of > 100% are not uncommon for incident light at wavelengths of 350 nm on poorly thinned devices. We have developed a thinning process that reduces the pixel-to-pixel variations to < 5% while maintaining a quantum efficiency (QE) of > 40% at 350 nm, when the back surface is charged. Two scientific CCDs are currently made with thiA process, a 404 x 64 array of 52 x 52 gm pixels and a 1200 x 400 array of 27 x 27 gm' pixels. Test results of this process on these two devices will be presented.
© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Rusty Winzenread, Pat Chiao, Weng-Lyang Wang, and Lloyd Robinson "Improved Uniformity In Thinned Scientific CCDs", Proc. SPIE 1161, New Methods in Microscopy and Low Light Imaging, (22 December 1989);


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