Wavelength selective and 3D stacked microbolometers for multispectral infrared detection



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Development of wavelength selective detection, tunable multi-spectral capability with functionality in the infrared spectral region is highly desirable for a variety of applications such as thermography, chemical processing and environmental monitoring, spectroradiometry, medical diagnosis, Fourier transform infrared spectroscopy, night vision, mine detection, military defense and astronomy. Infrared detector with wavelength selective functionality have emerged as next generation infrared detectors. This study presents fabrication and characterization of wavelength selective Germanium dielectric coated Salisbury screen and novel 3D stacked microbolometer for multispectral infrared detection. This novel fabrication process helps produce much flatter, more robust device structure by using an un-patterned sacrificial layer to produce device legs that hold the central structural layer above the reflective mirror supported by a completely flat sacrificial layer with sufficient thermal isolation to allow microbolometer operation. For the fabricated wavelength selective Germanium dielectric coated Salisbury screen microbolometer using self aligned process, the FTIR measured spectral responses and numerical simulation results show excellent agreement with wavelength selectivity (9[mu]m, 10[mu]m, 11[mu]m) in long wave infrared (LWIR) region. To achieve multicolor infrared detection, recently a few device concepts using uncooled detectors have been reported. However, none of the proposed device designs have demonstrated fabrication. Moreover, Commercial Fabry-perot resonant cavity based uncooled microbolometers (Air gap: 2 to 2.5μm) have limited design parameters due to multicolor narrow band spectral response. In this study, a feasible device fabrication method for novel 3D stacked microbolometer is demonstrated for multispectral uncooled infrared detector that can achieve tunable narrowband absorption in mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral regions.