Research On The Related Technology Of HgCdTe Infrared Focal Plane Detector Reliability

In the research field of infrared detector，infrared focal plane detector has obtained greatachievement in the performance, size etc with the rapid development of material growth technology,chip manufacturing technology and microelectronics technology. Countries all over the worldincreasingly pay attention to the infrared focal plane detector for the successful application in spaceremote sensing and military field. At present, the hybrid structure HgCdTe infrared focal planedetector is the most successful technology in the development of all kinds of infrared focal planedetector technologies. At present, there is a large technological gap between the internationaladvanced level and the domestic level on HgCdTe infrared focal plane array(IRFPA), especially insome key technologies of reliability for engineering application. To improve the engineeringapplication level of our HgCdTe IRFPA, shorten the gap with the international advanced level, it isnecessary to establish a reliability design platform.For the solving of reliability problems caused by thermal mismatch in hybrid structureHgCdTe IRFPA, the emphasis of this paper is the establishment of the characterization methods andmodels for thermal stress analysis of detector package structure, and using them in optimization anddesign of our long linear and large format HgCdTe IRFPA package structure, the main contents areas follows:1. Deformation measurement of IRFPA package structure in cryogenic temperature. A methodfor the measurement of thermally induced deformation of IRFPA packaging structure at cryogenictemperature has been developed. Deformation of the actual packaging structures in the packagingprocess has been measured by using this method. Comparison with measurement results andtheoretical calculation shows good agreement, validating the rationality of the measuring method. Inaddition, the deformation measurements are conducted for a number of backfilled devices ofdifferent batches.2. Study on modification of cryogenic epoxy resin for IRFPA packaging. The Nano-Al2O3/DW-3Epoxy resin composite has been prepared. The effects of particle sizes, contents ofNano-Al2O3on the coefficient of thermal expansion of DW-3Epoxy resin were studied. A modified DW-3Epoxy resin with lower coefficient of thermal expansion was prepared successfully when thecontent of Nano-Al2O3is2%~8%.3. Experimental study of IRFPA package related material parameters. A method for themeasurement of coefficient thermal expansion of materials in77K～300K range of temperature hasbeen designed. The Coefficient of thermal expansion, elastic modulus, and Poisson’s ratio ofmaterials involved in the IRFPA package is obtained. This will provide a sound reference data forthe IRFPA package structure design and process design.4. Effect of stress and strain on the performance of HgCdTe photovoltaic device. At a certainstress level, compressive stress results in the increase of the density of defects in the device surfaceand junction area, increasing the trap assisted tunneling current; Tensile stress has certain effect onimproving the trap assisted tunneling current; The effects of both compressive stress and tensilestress on the IV characteristic are reversible in some degree. It is proven that the high stress in theedge of HgCdTe chip has adverse effects on the reliability of the device, which provides a basis forthe package structure design of IRFPA。5. Optimization design of linear HgCdTe IRFPA package structure. The finite element modelsfor the structure design of direct and indirect linear hybrid HgCdTe infrared detectors have beenestablished. The thermal stress distribution and thermally induced deformation of the detectorassembly as a function of the thickness of each component, the materials properties of electricallead board in cryogenic temperature are analyzed. The package structure design features of thesetwo kinds of linear IRFPA were summarized, and the corresponding experimental verification wereconducted.6. Optimization design of large format HgCdTe IRFPA package structure. The finite elementmodel for the structure design of large format hybrid HgCdTe infrared detectors has beenestablished. The effect of the thickness of each component, the materials properties of electricallead board, and cold plate packaging on thermal stress and deformation of Si and GaAs substratedetectors were analyzed; Some improved methods were presented respectively according to theanalytical results for these two kinds of detectors, and these methods were verified by experiment.The experimental data provides reference for the structure design of these two kinds of HgCdTeIRFPA.