GOALI: Systems Integration of Uncooled YBaCuO IR Detectors

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9800062 Butler This proposal concerns the investigation and development of high detectivity pyroelectric infrared imagers operating at room temperature. Previous work supported by the National Science Foundation and Army Research Office has shown that semiconducting, thin film YBaCuO possesses a high pyroelectric coefficient at room temperature, two hundred times greater than other thin film materials. This enables high detectivity pyroelectric thermal detectors to be fabricated on micromachined thermal isolation structures integrated on CMOS read-out circuitry, since the amorphous semiconducting phase of YBaCuO, used in these imaging devices, is deposited at ambient temperature with no need of high temperature post-annealing. It has been demonstrated by researchers at Southern Methodist University (SMU) that surfacemicromachined Nb/YBaCuO/Nb capacitor structures are capable of exhibiting pyroelectric coefficients in the range of 65 nC/K cm2 without an externally applied electric field and in the absence of prior poling. When poled, the pyroelectric coefficient was found to increase to 18 (C/cm2-K. If integrated with state-of-the-art thermal isolation structures, background limited performance is achievable. High detectivity pyroelectric imagers will be fabricated by combining the SMU pyroelectric devices with the state-of-the-art thermal isolation structures and read-out circuitry produced by Raytheon/TI Systems. Various issues at the systems level must be addressed and solved including process compatibility, electrical compatibility, and system figures of merit. To solve the electrical compatibility issue, the resistive loss of YBaCuO will be decreased by adjusting its oxygen content. Process compatibility issue will be addressed by finding an appropriate electrode metal for YBaCuO that is CMOS compatible and designing a fabrication process that incorporates the principles of YBaCuO deposition and lithography with micromachining technology developed for the thermal isolation structu res at Raytheon/TI Systems. Several figures of merit, such as pyroelectric coefficient, pyroelectric figure of merit, responsivity, specific detectivity, noise, will be used to assess performance at the focal plane array level. The pyroelectric properties and the noise mechanisms, which limit the detectivity and are uniquely characteristic of the high degree of thermal isolation, will be investigated. Upon successful completion of integration at the focal plane array level, a systems-integration will be attempted towards a complete IR camera. The proposed work will realize a full range of engineering processes from basic research to device concepts to systems integration, thereby developing a complete uncooled IR imager, unsurpassed in performance and cost. ***