Effect of beam length on the uncooled microbolometer performance

Uncooled microbolometers are widely used for Infrared imaging including night vision camera for security and surveillance, weapon detection in military application and monitor temperature controlled industrial process. Recently, inexpensive, non-contact thermal detectors are high in demand for human body thermography in medical application. The thermal radiations produced by human body is very much low and require low thermal budget microbolometer with improved responsivity for microelectromechanical (MEMS) technology based thermal detectors. This paper presents the pyro-resistive mechanism based amorphous silicon microbolometer. There is always a tradeoff between responsivity and thermal time constant of microbolometer. The effect of beam length to reduce thermal budget and improve the responsivity is discussed in this paper. Microbolometer structures with 25 µm pixel size are designed and analyzed using CoventorWare. In accordance with the simulated results, the device with meander shape long beams showed maximum electrical responsivity of 7.24 × 105 V/W and short thermal time constant of 2.5 ms.