Thermal budget calculations, design aspects, and device performance of high-Tc air-bridged microbolometers

Abstract

The thermal properties of an air-bridged microbolometer have been evaluated on the basis of a finite element calculation scheme for the first time. The numerical results show that the performance of the device's sensitively depends on geometry and layout. The degree of thermal coupling and interaction with the heat sink affects the thermal time constant and frequency range of operation. For identical geometries, experimental and modeled data are in good agreement. The length of the air-bridge is defining the effective thermal time constant but has little effect on the thermal responsivity. An unusually high responsivity has been calculated for configurations where the thermal coupling to the heat sink has been minimized. This design leads to an increase of responsivity of a factor of 200 and would establish superior operation of the device even at ambient temperature.

Stability conditions, nonlinear dynamics, and thermal runaway in microbolometers

“…The heat transfer from the sensor element, and steady warming up of the surrounding heatsink has been verified recently by finite element calculations for a superconducting membrane based transition edge microsensor. 8 When G and C are considered to be varying with sensor temperature, the determination of T s , I b 2 , and V b 2 at the singularity condition is more difficult. The solution of the heat balance equation would require an iterative procedure.…”