Uncooled thin ®lm infrared imaging device with aerogel thermal isolation: deposition and planarization techniques

We have successfully integrated a thermally insulating silica aerogel thin ®lm into a new uncooled monolithic thin ®lm infrared (IR) imaging device. We have calculated noise equivalent temperature differences of 0.04±0.108C from a variety of PbxZryTi12yO3 (PZT) and PbxLa12xZryTi12yO3 (PLZT) pyroelectric imaging elements in these monolithic structures. The low thermal conductivity of the aerogel ®lms should also result in a signi®cantly faster temporal response as well. Fabrication of these monolithic devices entails sol±gel deposition of the aerogel, sputter deposition of the electrodes, and solution chemistry deposition of the pyroelectric element. Consistent pyroelectric response across the device is achieved by use of appropriate deposition and planarization techniques of these three layers. Adjusting the chemistry and deposition process of the aerogel thin ®lm had the greatest effect on large-scale uniformity and performance across the device. Sputter depositing a planarization layer on top of the aerogel offered only minimal improvement in reducing surface roughness. However, using solution chemistry to deposit multiple thin coatings of PZT for the imaging element resulted in a visible reduction in scattering and 80±100% pixel yield. q 1998 Elsevier Science S.A. All rights reserved.