Zifir-Altın Kaplamalı Soğutmasız Bolometrelerin Optik Modellenmesi
Toğrul, Zeynep Çiğdem
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Microbolometer based uncooled infrared cameras have been used mostly in industrial, civilian and military applications. With the increase in detectivity values, these cameras have begun to take the place of cooled cameras, which are very difficult to maintain and use, and at the same time very expensive. As market share of uncooled cameras grows day by day, interest shown in microbolometer technology is also increasing. The main objective of this interest is to reduce production costs. In order to reduce the cost, sensor layers based on hydrogenated amorphous silicon (a-Si:H) technology which can be produced by CMOS processes are used. However, this material requires the use of an additional absorber layer due to its low infrared absorbance. Materials such as silicon dioxide and silicon nitrure are used as the absorber layer which are also suitable with CMOS process, in existing structures in the market. In this thesis, applicability of gold-black coating providing very high absorption on both the medium and far infrared bands, on the a-Si:H sensing layer is evaluated. In order to make this evaluation, optical models of all layers of microbolometer have been obtained. In addition to that, infrared absorbance of a multilayered microbolometer in the desired band was also calculated by obtained model. A virtual test environment has been established for the measurement of performance parameters such as detectivity and thermal time constant. In this virtual test environment, gold-black, silicon dioxide, silicon dioxide and silicon nitrure absorbing layers were coated on a-Si:H and comparative tests were carried out. As a result of this study, it has been shown that the designed gold-black coated microbolometer structure has a detectivity of 5 times higher than other coatings in a design with a speed of 30 frame per second.