Improvement of uncooled infrared imaging detector by using mesoporous silica as a thermal isolation layer

Thermal-insulation properties of ordered mesoporous silica could possibly improve the efficiency of uncooled infrared imaging detector by introducing a mesoporous silica layer between TiN absorber and Si₃N₄ passivation layer. IR absorption rate of 50% porosity mesoporous silica was simulated and the results showed that above 90% infrared absorptance could be achieved in 8-12 μm wavelength region. Thermal conductivity of mesoporous silica was measured by 3ω method. Finite element modeling was used to simulate thermal isolation effect of mesoporous silica inserted structure. The result shows that an effective thermal-insulation effect could be obtained with 150 nm thick mesoporous silica layer. Also according to the simulation result of time transient temperature variation, it was found that mesoporous silica layer for thermal isolation induced an increase of 30% of residual temperature on TiN absorber. The mesoporous silica film was found to be a good thermal isolation layer for microbolometer.