An effective thermal conductance tuning mechanism for uncooled microbolometers

With the increasing demand on infrared (IR) detectors for imaging harsh environment processes, widening the application range of uncooled microbolometer arrays has become an important research area. An efficient way of increasing this range is tuning the thermal conductance of the microbolometer array using electrostatic actuation, which is usually achieved by directly applying an actuation voltage to the substrate. However, this method does not allow pixel-by-pixel actuation, limiting the tunability. In this paper, we present a new method of actuation which uses the micromirror located below the microbolometer as the actuation terminal. We demonstrate that using micromirror actuation, the thermal conductance can be tuned by a factor of three. An analytical model to calculate the thermal conductance of this new type of microbolometer is presented. Results of the model are compared to finite element simulations and experimental measurements on a test structure fabricated for this purpose, showing good agreement. The new tuning mechanism provides a fairly linear thermal conductance tunability, thus making it a promising thermal conductance controlling mechanism for adaptive IR detectors.