Ultra-shallow EUV and soft X-ray gratings fabricated by broad-beam nitrogen ion irradiation

TL;DR

This paper presents a novel method for fabricating ultra-shallow diffraction gratings with nanometer-scale heights using broad-beam nitrogen ion irradiation, enabling precise control for EUV and soft X-ray applications.

Contribution

It introduces a controlled ion irradiation technique to create nanostructures in silicon, expanding fabrication capabilities for EUV and soft X-ray gratings.

Findings

Fabricated gratings with heights from 1 nm to 10 nm.

Ion energy variation allows control over structure height and shape.

Method offers a precise alternative to dry etching for nanostructure fabrication.

Abstract

Controlled and precise fabrication of structures with heights in the range of single digit nanometres is one of the challenges for diffraction gratings operating near-normal incidence in the extreme ultraviolet (EUV) and soft X-ray range. Here, we expand on previous research utilizing swelling of silicon after irradiation with ions as alternative to conventional dry etching. By irradiating silicon through a mask with a broad beam of nitrogen ions, we realized lamellar gratings in a precise and well controlled process. We were able to fabricate gratings with structure heights between (1.00 +/- 0.05) nm to (10.0 +/- 0.5) nm and a pitch of 1 micrometre, which is suitable for both EUV and soft X-ray applications. A variation of ion energy from 20 keV to 40 keV further expands the foundations of this process and yielded an additional parameter to control the resulting structure height and shape.