Microbolometer Detector Array for Satellite-Based Thermal Infrared Imaging

An infrared imaging array based on micromachined bolometric detectors is under development. The array is designed to meet the requirements of satellite-based infrared imaging and detection applications, including cloud and earth surface temperature monitoring and forest fire monitoring. Its design makes it also suitable for terrestrial spectrometric and moderate speed imaging applications. The array consists of three parallel lines of 512 pixels on a 39 µm pitch. Each pixel includes both active and reference detectors to reduce pixel to pixel offset variation, eliminate common mode bias noise, and provide increased immunity to die temperature drift. The thin films making up the active detector structure are designed to provide high and uniform infrared absorption between 8.3 and 13 µm. The pixels are fabricated monolithically over a custom CMOS readout integrated circuit (ROIC) using a surface micromachined post-processing approach. The advanced ROIC integrates the signals of all pixels in parallel using switched capacitor correlated double sampling integrators and performs on-chip analog to digital conversion. Despite the small pixel size the projected thermal resolution over the 8-12 µm spectral band for f/1 optics is below 50 mK. In this paper we will describe the detector array design and present preliminary test results.