Preparation and characterization of thick porous SiO2 film for multilayer pyroelectric thin film IR detector

Porous SiO2 film is used as a thermal-insulation layer to block the diffusion of heat flow from the pyroelectric layer to the silicon substrate in multilayer pyroelectric thin film IR detector. It is important that porous SiO2 film is uniform, smooth, crack-free, thick and high porosity in order to integrate other films to make IR detector having high specific detectivity (D*). In this paper, thick porous SiO2 film is prepared via sol–gel method with tetraethyl orthosilicate (TEOS), H2O, C3H5(OH)3, NH3·H2O as precursors. The thickness and refractive index of porous SiO2 film are measured by Thin film Measurement System (Model: Filmetrics, F20). The surface condition is measured by Atomic Force Microscopy (Model: DI, Nano-scope III) and the Scanning Electron Microscopy (Model: JEOL, JSM-5510). Experiment results show that the thickness of porous SiO2 film up to 3 μm can be obtained. Porosity of the film up to 59% and nanometer size pore can be achieved by one spin coating after annealed at 550 °C for 30 min. The surface roughness of porous SiO2 thick film is about 7.25 nm. The thick porous SiO2 film is smooth and crack-free. The electrical properties of thick porous SiO2 film are also measured.