Device-level vacuum packaged uncooled microbolometer on a polyimide substrate

Uncooled infrared detectors (IR) on a polyimide substrate have been demonstrated where amorphous silicon (a-Si) was used as the thermometer material. New concepts in uncooled microbolometers were implemented during the design and fabrication, such as the integration of a germanium long-pass optical filter with the device-level vacuum package and a double layer absorber structure. Polyimide was used for this preliminary work towards vacuum-packaged flexible microbolometers. The detectors were fabricated utilizing a carrier wafer and low adhesion strength release layer to hold the flexible polyimide substrate during fabrication in order to increase the release yield. The IR detectors showed a maximum detectivity of 4.54 × 106 cm Hz1/2/W at a 4 Hz chopper frequency and a minimum noise equivalent power (NEP) of 7.72 × 10−10 W/Hz1/2 at a biasing power of 5.71 pW measured over the infrared wavelength range of 8-14 μm for a 35 μm × 35 μm detector. These values are comparable to other flexible microbolometers with device-level vacuum packaging which are found in literature.