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23 April 2020 Development of new pixel structure for beyond 12-μm pixel pitch SOI diode uncooled IRFPAs
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Abstract
We developed silicon-on-insulator (SOI) diode-based uncooled infrared focal plane arrays (IRFPAs), in which single-crystal pn junction diodes formed in an SOI layer are used as temperature sensors. These diodes, based on silicon large-scale integration technology, offer excellent uniformity, and have led to the use of high-performance uncooled IRFPAs in a wide variety of applications. In order to extend the pitch to less than 12 μm, a scalable new pixel structure has been developed to reduce the pixel size, based on a novel thermally isolated structure, which is fabricated above a CMOS processed wafer. The pn junction diodes used as a temperature sensor are separated from the underlying substrate by supporting legs made from thin metal wire, forming a cavity. To reduce the pixel size, we are developing a new diode structure by optimizing the ion implantation condition, thinning the SOI layer, and redesigning the supporting legs, achieving a smaller pixel size even with ten serially connected diodes. We also evaluated a new readout circuit architecture that enables an increase in sensitivity by generating a larger change in the diode forward voltage at a given temperature with no change in the number of diodes in the SOI layer. The effectiveness of the proposed readout circuit architecture was verified using a fabricated test element. The sensitivity of the test element was 128% of that for existing circuit structures, and further increases are expected with circuit structure optimization. These techniques have greatly enhanced the performance of our SOI diode based uncooled IRFPAs.
© (2020) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
D. Fujisawa, M. Hanaoka, Y. Kosasayama, A. Yutani, K. Shintani, H. Hata, M. Ueno, T. Takenaga, and M. Yamamuka "Development of new pixel structure for beyond 12-μm pixel pitch SOI diode uncooled IRFPAs", Proc. SPIE 11407, Infrared Technology and Applications XLVI, 114071A (23 April 2020); https://doi.org/10.1117/12.2558287
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