Investigation on Performance and Vacuum Package of MEMS Infrared Focal Plane Arrays

A substrate-free microelectromechanical system (MEMS) focal plane array (FPA) has been successfully developed. Since there is no silicon substrate beneath the FPA´s pixels, the infrared radiation (IR) loss has been significantly reduced. However, at ambient pressure, it is difficult to obtain a clear visible image due to the sensitivity loss caused by the thermal conductance of air. To improve the packaged FPA´s performance, its thermal sensitivity and response time were investigated under varying air pressure. The high-contrast IR thermal images of a human hand were captured at room temperature and under an air pressure of 0.01 Pa, and the noise-equivalent temperature difference of the FPA was also estimated to be about 373 mK compared with the 1.4 K under a pressure of 10 Pa. What is important is that the FPA´s response time was increased from 50.1 to 336.6 ms by the decrease in air pressure. In addition, we present an approach to package the MEMS FPA at a low-pressure vacuum with two optical windows, which is an effective way to increase FPA´s sensitivity.