Achieving unlimited recording length in interference lithography via broad-beam scanning exposure with self-referencing alignment

Donghan Ma,Lijiang Zeng,Yuxuan Zhao

doi:10.1038/s41598-017-01099-3

Abstract

Large-area holographic gratings are of great importance in diverse fields including long-range interference metrology, high-resolution astronomical telescopes, and chirped-pulse-amplification systems. However, in conventional interference lithography, the recording length is limited by the aperture of the collimating lenses. Here we propose broad-beam scanning exposure which employs the latent grating generated continuously during scanning for real-time dynamic fringe locking and thus achieves unlimited recording length. This method is experimentally proved to make high-quality gratings, and is expected to be a new type of interference lithography.

Highlights

Large-area diffraction gratings play an important role in long-range interference metrology[1], high-resolution astronomical telescopes[2], and chirped-pulse-amplification systems[3, 4]
One area of the substrate is exposed by the small-size interference field at a time, and the substrate moves to the position for the exposure
In order to keep the wavefront of adjacent exposure areas continuous, it is vital to adjust the phase and attitude of the exposure fringes relative to the substrate between adjacent exposures

Summary

Introduction

Large-area diffraction gratings play an important role in long-range interference metrology[1], high-resolution astronomical telescopes[2], and chirped-pulse-amplification systems[3, 4]. Near-field scanning exposure was proposed by Jourlin et al.[16,17,18], where an expanded laser beam illuminated a transmission grating to generate interference fringes for exposure They used a grating scale nearby to measure the position of the substrate, and modulated the intensity of the exposure interferogram . In 2015 we reported our work on broad-beam scanning exposure along the grating vector to make gratings with low stray light[20] In this method, one half of the interference field was used for exposure, and the other half was used to illuminate the reference grating alongside the substrate for phase and attitude alignment. This method is expected to be a new type of interference lithography

Methods

Results

Conclusion