Thermal-impedance simulations of antenna-coupled microbolometers

Antenna-coupled microbolometers have shown characteristics that makes them a promising option for fast-frame-rate infrared-imaging applications, however commercial application of these type of devices is only possible if a substantial increase in their responsivity is achieved. Due to the fabrication requirements of these detectors the process of optimizing them becomes extremely expensive and time consuming. In this paper a finite-element-based simulation approach to optimize the design of thermally isolated microbolometers is presented and the particular case of a bowtie-coupled microbolometer on a silicon nitride membrane is analyzed. The thermal impedance simulations performed indicate that a responsivity increase of at least a factor of 6x can be obtained by optimizing the membrane shape and the materials used for the bias lines, this would lead to values of D* close to 1 x 109 cm root Hz/W if applied to devices reported in the literature, which would close the gap between the responsivity of antenna-coupled detectors and detectors used in commercial infrared imaging systems.