Miniaturization of grayscale images

Abstract

Printing of binary patterns onto substrates has been the strength of resist-based binary lithography that has advanced the semiconductor industry. When patterning grayscale structures however, grayscale-lithography processes that are often difficult to use are considered. Here, we describe a process using binary-lithography to create arbitrary grayscale patterns. Particularly, we demonstrate a novel algorithm for the miniaturization of grayscale images that preserves grayscale information when imaged in a scanning electron microscope (SEM). The brightness level of each pixel was adjusted by controlling the density of nanometer-scale pixel elements. Using 17 shades of gray, we demonstrate the electron-beam lithography patterning of an M.C. Escher mezzotint and the Lena image with pixel elements consisting of 10-nm-diameter nanoposts spaced by gaps as small as 10 nm. The patterned images were tens of microns in size and faithfully reproduce the original images under SEM inspection. The process described could find applications in the fabrication of deep sub-wavelength elements with gradually varying dimensions in nanophotonic devices, and in creating grayscale images as anti-counterfeit features on substrates.