Processing, Fabrication and Characterization of Advanced Target Sensors Using Mercury Cadmium Telluride (MCT)

Report No. ARL-TR-5292
Authors: F. Semendy, G. Brill, P. Wijewarnasuriya, Y. Chen, J. Sun, J. Bickford, and N. Bambha
Date/Pages: September 2010; 22 pages
Abstract: In this report the growth, processing, fabrication, and characterization of HgCdTe (or mercury cadmium telluride [MCT]) infrared (IR) detectors for advanced target detection are reported. The material was grown by solid source molecular beam epitaxy (MBE). Grown materials were characterized prior to processing to obtain information on carrier concentration, mobility and resistivity. Inductive coupled plasma (ICP) etching and metallization as required by the design of the sensors at different levels of processing were carried out using either AZ 5214 or AZ 9245 as photoresist masks. For the first time spin coating and lithography parameters were optimized with AZ9245 as the photoresist mask to achieve smooth surface and vertical side walls. An etch-through process of MCT and Si with a combined thickness of about 510 µm deep was carried out by ICP etching first by Ar/H2 gases followed by covering the sample by a thick AZ 9245 photoresist mask and Bosch process using SF6 , O2 and C4F8 to detach the device from the base carrier silicon substrate. To understand the nature of the etching and to protect the surface of the detector, the wafers were periodically withdrawn and thickness of the photoresist measured. A twenty-step process finally yielded the desired ring type detectors that were used for electrical characterization and testing for target detection. The results of extensive steps involved in processing, device fabrication, material, and device characterizations are reported.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2010