Preparation and characterization of thick porous SiO 2 film for multilayer pyroelectric thin film IR detector

Abstract

Porous SiO 2 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 SiO 2 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 SiO 2 film is prepared via sol–gel method with tetraethyl orthosilicate (TEOS), H 2O, C 3H 5(OH) 3, NH 3·H 2O as precursors. The thickness and refractive index of porous SiO 2 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 SiO 2 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 SiO 2 thick film is about 7.25 nm. The thick porous SiO 2 film is smooth and crack-free. The electrical properties of thick porous SiO 2 film are also measured.