Advanced microbridge structure for reduced thermal conductivity in uncooled infrared microbolometers

The recent advancement of microbolometers, as a representative uncooled thermal sensing technology, has significantly promoted the development of low cost infrared imaging systems for both military and commercial applications. In this work, we experimentally demonstrated an uncooled infrared bridge microbolometer using beams with constant strength (BCS) design that simultaneously achieves low thermal conductivity and high mechanical integrity. A comprehensive analytical model is established to optimize the stress distribution along the supporting beams, yielding a reduced standard deviation of maximum first principal stress to 5.5 MPa and 13.7 MPa for single-layer and multi-layer configurations, respectively. Numerical simulations further address the analytical approximations and refine these results, lowering the stress variation to 4.997 MPa in the multi-layer beams. Experimental validation of the BCS design demonstrated a 3.53-fold improvement in readout voltage under vacuum compared to conventional constant-width beams, achieving a responsivity of 1.4 × 10⁵ V/W. This work demonstrates enhanced responsivity of BCS geometry in microbolometer design, offering a promising route for thermal conductivity management and structural optimization methodologies in next-generation complex infrared sensing systems.