Device-level vacuum packaged uncooled microbolometer on a polyimide substrate

Abstract

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 4.54×106cmHz1/2/W at a 4Hz chopper frequency and a minimum noise equivalent power (NEP) of 7.72×10−10W/Hz1/2 at a biasing power of 5.71pW measured over the infrared wavelength range of 8–14μm for a 35μm×35μm detector. These values are comparable to other flexible microbolometers with device-level vacuum packaging which are found in literature.