Technique for 25 nm x-ray nanolithography

Abstract

The image-forming limit of x-ray lithography is said to be ∼70 nm using existing devices and technologies. This article presents methods to extend the limit to 25 nm or even below. Preparatory to the study, a light source was designed to improve x-ray beam toward shorter wavelength. In addition, a simulation code has been developed to evaluate the methods. The first method is to use a mask with a larger period and pattern than deigned images. The mask forms the designed images with an enlarged period. Two-dimensional, 25 nm width images can be formed using a 100 nm period pattern mask at 8 μm gap. The second method is to use a mask with interference slits. Since the image pattern is sharply focused, ⩽25 nm images can be formed at 8–12 μm gaps. Multiple exposures are applied to both methods in order to fill in the clearances of the images. Simulation results are shown in both methods for typical patterns.