Design and characterization of adaptive microbolometers

Abstract

We report the first practical results on design and characterization of adaptive microbolometers with a thermally tuned responsivity. Such devices are needed to simultaneously image scenes that contain objects at ambient and extremely hot temperatures. In the high detectivity state, the microbolometers are operated similar to standard commercial devices. In the low detectivity state, portions of the support beams are brought in contact with the substrate, which thermally shorts the devices on a pixel-by-pixel basis. This is the first time this concept has been practically implemented in a microbolometer device architecture as opposed to simple cantilever beams and plates. The maximum actuation voltage is set to 17 V, and the thermal conductances, responsivities and detectivities of a typical device can be switched more than an order of magnitude between 1.

Electrostatically driven collapsible Au thin films assembled using transfer printing for thermal switching

“…On account of these characteristics, they are indispensable in sensing, actuation, and switching in micro/nano-devices. [1][2][3][4][5][6][7][8][9] While a few devices can be fabricated using wafer-level direct bonding, 4 most suspended films in such devices are fabricated by film deposition followed by etching of the sacrificial layers. Such fabrication is known to generate "fabrication stiction" problems, where thin films are pinned to substrates during aqueous rinse and dry cycles.…”

Modeling of thermal conductance in an uncooled microbolometer pixel

“…From these two figures, it can be observed that the thermal conductance is overestimated when using Eq. (5) and when the proposed model does not take into consideration the constriction resistance. On the other hand, as it was mentioned in Section 3.2, when the model includes the constriction resistance, the thermal conductance is underestimated due to the 2D channel approximation.…”

“…Therefore, careful consideration of the thermal conductance parameter is required at the design stage to optimize sensitivity without compromising speed. Current methods to estimate the thermal conductance in microbolometers only consider the temperature drop within the arms themselves [3][4][5]. However, as will be demonstrated later, the thermal conductance parameter depends on the plate dimensions as well.…”

An analytic model employing an elliptical surface area to determine the gaseous thermal conductance of uncooled VOx microbolometers

“…Although VO x microbolometers are mostly used as detectors under vacuum conditions to achieve high sensitivity, drawbacks exist when capturing scenes with high thermal dynamic range or high temperature regions like explosions, fire, fuselage and the sun [14,15]. The output of these sensors saturate and take a long time to recover.…”