Novel technology for microlenses for imaging applications

Microlenses are an important functional element of a modern imaging device. Typically, they are fabricated from organic materials on top of individual pixels. Though they are widely used, they do exhibit a number of limitations. These are, but not limited to, thermal stability, radiation sensitivity, outgassing properties, additional topography, and difficulty in manufacturing asymmetrical, noncircular microlens designs using conventional manufacturing techniques. In this paper, we present a novel approach for the fabrication of microlenses. We report on the design, manufacturing, and characterization of microlenses fabricated from classical dielectric materials used in the manufacturing of CMOS semiconductor devices. These microlenses rely on a Fresnel optical design, provide functionality similar to the classical microlenses, and do not suffer from their limitations. We subjected these microlenses to several environmental reliability stress conditions, including pressure, temperature, humidity, and their variation. Moreover, we test their sensitivity to gamma rays and protons.