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We report on the details of inductively coupled plasma etching for achieving low dark current long-wavelength infrared focal plane arrays (FPAs). External factors that influence the etching process are studied. A high-quality hard mask for excellent pattern transfer is discussed. Next, a suitable mounting technique for good thermal contact is described. Finally, the challenges and differences between etching large 200-μm test diodes and small 28-μm FPA pixels are discussed. The complete etching process is then demonstrated on a 320 × 256 complementary barrier infrared detector FPA. The mean dark current density of 2.2 × 10-4A/cm2 is measured at an operating bias of 128 mV with a 50% cutoff wavelength of 8.8 μm. Good imagery is achieved with an array yielding an 81% fill factor with 97% operability. Operating at T = 80 K, the measured mean noise equivalent differential temperature is 18.6 mK, and the mean detectivity is D* = 1.3 × 1011cm-Hz1/2/W.
Date of Publication: Sept.15, 2012