Research On Integrated Technology Of Optical Cover Wafer Of Uncooled Infrared Focal Plane Array

The optical cover wafer is an important component structure in the wafer-level packaging design,which has the functions of forming a vacuum sealed cavity,keeping a low vacuum level,and providing an optical interface.Aiming at the packaging requirements of uncooled infrared detectors,this paper proposes a new integrated design scheme,which is to prepare infrared metasurface flat lens and non-evapotranspiration thin film getter in the optical cover wafer.The infrared metasurface plate lens works in the far-infrared band?8-14?m?.It not only provides the optical interface,but also has the convex lens imaging function,which has a positive effect on reducing the detector size.Based on the existing material system,a non-evapotranspiration film getter which can be activated at low temperature?300??is designed.The main contents of this paper are as follows:?1?According to the working principle of uncooled infrared focal plane detector,this paper explains the necessity of vacuum sealed environment and optical interface for detector,introduces the characteristics and shortcomings of wafer-level packaging,and puts forward the integrated design of optical cover wafer.?2?Based on CST Studio Suite electromagnetic simulation software,the geometric parameters of four microstructural units are simulated,the corresponding transmittance and phase modulation values are obtained,and the microstructural unit database is established.Combining with the microstructural unit database,the arrangement algorithm of microstructural units of infrared metasurface plate convex lens is given by using generalized Snell's law and grating equation.?3?This paper compares the existing non-evapotranspiration thin-film getter material systems,and selects TiZrV alloy as the material of low-temperature activated thin-film getter.Two kinds of thin film getters Ti₂₀Zr₄₀V₄₀ at.%and Ti₂₅Zr₃₀V₄₅ at.%are prepared by magnetron sputtering.Through SEM morphology detection and thermal conductivity change in the shell cavity with getter,Ti₂₀Zr₄₀V₄₀ at.%getter can be activated at low temperature?300??,and its performance is better than Ti₂₅Zr₃₀V₄₅ at.%getter.?4?In this paper,an infrared metasurface flat convex lens and a light deflector are prepared.The focal spot diameter and focal length of the flat convex lens and the deflection angle of the light deflector are measured by optical experiments under the irradiation of CO₂ laser,which wavelength is 10.6?m.According to the experimental results,the hexagonal lattice cylindrical flat lens has a focal length of 40.76mm and a focal spot size of 139.97?m.Compared with the other two structures,the focal length is closer to the theoretical value and the light gathering performance is better.Therefore,the hexagonal lattice cylinder is more suitable as the microstructure unit of the far-infrared?8-14?m?metasurface convex lens.Finally,according to the preparation process of the infrared flat lens and the thin film getter,the overall design scheme and process flow of the optical cover plate are completed.