Dual-band Infrared Detector Wavelength Tunable Structure Research

With further development of modern focal plane technology, the single-band microbolometer technology is much more advance. However, there is limitation for the single-band microbolometer because it works in a unique band. In the military field, when the single-band microbolometer gets information of the target, it may make mistakes because of the target disguise (such as the information is weakened, the band is moved and so on), which would reduce the accuracy and reliability of detection. In order to avoid those mistakes, the dual-band microbolometers, which can simultaneously response in the two bands of3～5μm and8～10μm, comes into being.This article focused on the wavelength adjustable structure of dual-band microbolometer. The IntelliSuite software was used to simulate the electrodynamics characteristics of the adjustable structure. Combined with the current process technology, the process and basic parameters of material was determined and the masks were designed. The influence of the shape and the width of the bridge on the device mechanical properties was analyzed to obtain the optimal structure.For the pros and cons of dual-band microbolometer, the infrared absorption rate of the device surface is an important optical parameter. By investigating the influence of the layer thickness of multilayer films on the infrared absorption rate through Matlab, especially the sacrificial layer and silicon nitride passivation layer; the optimal thickness was achieved.In this paper, some basic theories on preparation process, such as the photolithographic process, the thickness of photoresist, the uniformity and stay rate of films have been introduced. The dual-band microbolometer with adjustable structure has been fabricated through the optimization of technological parameter. By testing the morphology and flatness of the device via microscope and scanning electron microscopy, the deformation of adjustable structure with different micro-bridges was compared; then the performance of dual-band microbolometer was improved.