Silicon lens arrays for wafer level packaging of IR-sensors

Abstract

A new process technology has been developed for a cost efficient production of refractive convex lenses made of silicon. These lenses are produced as lens arrays on standard eight inch Si-wafers to allow the optical capping of IR sensors in a wafer level packaging (WLP) process. A manufacturing process is described using a glass forming process with thin (50um) AF32® glass wafers. Si-spheres of well-defined diameter are transferred to a thin glass membrane on top of a Si-wafer with prefabricated cylindrical openings. In a thermal bonding process, the lens part of the Si-spheres sinks into the cavities while the outer part is grinded away. The resulting plano-convex lens calottes remain firmly embedded in the wafer surface. In this manner an array of Si-lenses on a Si-wafer is realized to be used as cover wafer for wafer level packaging of IR-sensor devices. First designs of Si-lens arrays have been fabricated. Starting with Si-spheres of radius of curvature 0.8 mm conv ex lenses of 0.82 mm diameter (aperture) and a sagittal height of 0.12 mm were produced