Nanostructured Color Filters for CMOS Image Sensors

Abstract

Digital color imaging relies on spectral filters on top of a pixelated sensor, such as a CMOS image sensor. The resolution of the image sensor depends on the pixel size. To improve the imaging quality, smaller pixel and spectral filters are therefore required. Dielectric nanostructures, due to their resonant behavior and its tunability, offer the possibility to be assembled into miniature spectral filters, which could potentially replace conventional pigmented and dye-based color filters. In this letter, we designed a color filter based on a rectangular metal aluminum array structure, with a thickness of only 125nm, about one-eighth of a conventional chemical color filter. The influence of array cycle, dielectric layer structure and other parameters on the transmission spectrum and the color filter characteristics were investigated using the Finite Difference Time Domain. By numerical simulation, at a pixel size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.2~\mu \text{m}$ </tex-math></inline-formula> , the transmittance of RGB is as high as 82%, 70%, and 91%. The nanostructured color filter can have potential applications in the field of high-resolution color imaging.