Micromachined infrared bolometers on flexible polyimide substrates

Abstract

Micromachined infrared sensor arrays have been fabricated on flexible polyimide substrates using a silicon wafer carrier during the fabrication process. These flexible polyimide substrates containing the micromachined infrared sensors were removed from the silicon wafer at the end of fabrication. The fabrication technique utilized surface micromachining of a bridge structure to form the thermal infrared (IR) sensors on flexible substrates. Semiconducting yttrium barium copper oxide YBCO was used as the radiation sensitive material. 1 × 10 sensor arrays of microbolometers were micromachined using a photo-definable polyimide sacrificial layer and characterized before and after removal of the substrate from the Si wafer carrier. The flexible infrared microsensors showed similar performance to microbolometers fabricated on rigid silicon substrates. The YBCO thermistors exhibited a temperature coefficient of resistance (TCR) of −3.4% K−1 near room temperature. Responsivity and detectivity values as high as 6.1 × 104 V/W and 1.2 × 108 cm Hz1/2/W, respectively, were measured in vacuum for a 40 μm × 40 μm microbolometer with 1 μA bias. The lowest observed noise equivalent power was 4.1 × 10−11 W/Hz1/2 while the lowest thermal time constant was 5.7 ms.