Micromachined infrared sensor arrays on flexible polyimide substrates

This paper presents work on micromachined infrared detectors on flexible substrates. The detectors are made of semiconducting yttrium-barium-copper-oxide (YBCO) and are built on a 40-50 μm layer of polyimide (PI58578G) that serves as the flexible substrate. Two variants of micromachined infrared detectors have been fabricated The first variant employs a mesa structure in which self-supporting Ti arms hold up the detector pixel. The second variant has a more planar topology with the detector being supported by a layer of silicon nitride. Surface micromachining is used to isolate the detectors from the substrate. After fabrication the polyimide is peeled off the carrier wafer and the devices are packaged and characterized. The 40×40 μm² microbolometers have responsivities ranging from 7.4×10³ V/W to 10⁴ V/W and detectivities ranging from 6.6×10⁵ cm-Hz¹2//W to 10⁸ cm-Hz¹2//W. These results are comparable to those obtained for devices made on a rigid silicon substrate. The effect of substrate heating is also investigated and found not to affect the detector performance.