Design, Simulation and Characterization of Wheatstone Bridge Structured Metal Thin Film Uncooled Microbolometer

It is demonstrated for the first time that the Wheatstone bridge structured metal thin film resistive uncooled microbolometer (in short, WB-bolometer) provides promising temperature sensitivity. This paper describes the design, simulation, and characterization of WB-bolometer using titanium nitride (TiN) thin film as the infrared (IR) sensing material. TiN thin film is designed into four resistors which are connected to each other in Wheatstone bridge configuration. The resistance value of each resistor changes with different rates upon IR absorption, which can be attributed to the difference in their associated thermal conductance. As a result, the bridge output voltage varies in response to the absorbed IR power. Simulation was employed to compare and characterize different designs of WB-bolometer. It was found that design with two sensing elements has the optimum performance. The proposed WB-bolometer is also capable of operating at elevated temperatures (> 250 oC) due to its adjustable and small initial offset voltage with minimum associated noise.