Fabrication of 53.2 nm pitch self-traceable gratings by laser-focused atomic deposition combined with extreme ultraviolet interference lithography

Abstract

The period of the self-traceable grating has extremely high accuracy and minimal uncertainty due to its traceability to natural constants. It is an essential task to shorten the period of self-traceable grating to below 100 nm. In this paper, the self-traceable Cr grating with a period of 212.8 nm prepared by laser-focused atomic deposition (LFAD) is used as the mask, and the second-order frequency doubling (k=2) of the Cr grating is performed by extreme ultraviolet interference lithography (EUV IL). The Cr grating is designed for the best second-order diffraction efficiency. By optimizing the orthogonality between the laser standing wave and the atomic beam, a Cr grating with a peak-to-valley height of 60 nm is prepared. After exposure and development with PMMA 672.01 photoresist, the Si grating is finally obtained by pattern transfer. And its average pitch is evaluated as (53.2 ± 0.1) nm. The exposure results of different photoresists and the uniformity of grating patterns are discussed. The peak-to-valley height of the Si grating is about 50 nm, and the full width at half maximum is about 20 nm. This research provides the possibility for the wider application of self-traceable gratings in advanced nanofabrication and precision measurement.