Proximity X-ray Nanolithography

Abstract

The use of x-ray lithography in the fabrication of integrated electronics at 0.5 μm minimum feature sizes, and its extension to 0.1 μm features, is well documented in the technical and popular literature. The primary advantage of x-ray relative to optical-projection lithography in the 0.5 to 0.25 μm range is process latitude, which follows from a high contrast aerial image and absence of coherent scattering (e.g., standing waves). The potential of x-ray lithography in the nanometer domain (i.e., sub-100 nm features) has been appreciated since the late 70's when 18 nm lines and spaces were demonstrated by Flanders [1]. Over the past 5 years, a concerted effort to develop a reliable, manufacturing-compatible technology for sub-100 nm lithography has been persued at MIT; our motivation being the eventual manufacture of quantum-effect electronic systems. A number of options were considered. Our results indicate that x-ray nanolithography using 1 to 1 masks will meet all the needs of manufacturing down to 50 nm features, and probably also from 50 down to 10 nm. The techniques of x-ray nanolithography will be reviewed and the factors that limit resolution and drive mask architecture described.