| Summary: | 碩士 === 國防大學理工學院 === 光電工程碩士班 === 100 === In this thesis, the study is addressed in the use of selectively wet-etching directly to promote the thermal imaging performance of quantum well infrared photodetector (QWIP) after roughly mechanical etching process on backside GaAs wafer. For the treatment of two-step selectively wet-etching using (NH4OH:H2O2 or H3PO4:H2O2) and (C6H8O7: K3C6H5O7‧H2O: H2O2) recipes, the bonding strength of Al-O on the AlxGa1-xAs materials is larger increasing in the Al mole fraction, contrast with the bonding strength of Ga-O and As-O on the GaAs materials. For this situation, the mechanism of selectively wet-etching has been generated, and it results in Al2O3 production on the surface of AlxGa1-xAs materials to stop wafer etching process. While the backside FPA substrate is thinned to less than 1μm, the better performance of thermal image, higher uniformity, lower noise equivalent differential temperature (NEDT), and substrate leakage-current have been shown. The process methodology for QWIP FPA is being developed to meet the need of commercialization in recent ten years. For the cost-down issue of the fabrication of QWIP FPA, it is proposed successfully using the two-step selectively backside wet-etching directly is alterative for simplifying the QWIP backside-thinning process. The high performance infrared image taken from QWIP FPA with this proposed process is comparable to the conventional one with the mixture of wet- and dry- etching ICP-RIE. For increasing the accuracy of backside etching and surface uniformity on the GaAs/AlGaAs materials, we have to choose good selective wet-etching recipe, with modifying the pH values of etchant to establish its standard quantity for making etching rate and selectivity more stable and getting depth of optical grating more accurate, better uniformity on AlGaAs layer then raising the responsivities without the use of expensive dry-etching facility and with needless of complicated process. Also, using this wet-etching recipe, we have proposed, the conventional QWIP structures combined with the etching stop of AlxGa1-xAs materials, the increasing absolute responsivties with the better control on accuracy for the depth of optical grating. We have successfully proposed the high performance long-wavelength infrared image, using selectively wet-etching recipe to thin the backside of focal plane array (FPA) on GaAs substrate, solve the distortion of optical crosstalk without thinning substrate, and remove the dislocations and pinholes induced by delaminating and image deterioration due to the thermal stress and lattice–mismatch between GaAs-based FPA and silicon-based readout integrated circuit (ROIC) while the stirling-cooling temperature is recycling for QWIP FPA imaging module. We also have shown the higher FPA leakage current without non-backside selectively wet-etching thinning process increasing Vdetcom biases of ROIC.
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