# Design and Fabrication of Continuous Surface Optical Field Modulator for Angular Spectrum Discreteness Compensation

## TL;DR

This paper presents a new optical modulator design to improve light uniformity in lithography machines by compensating for angular spectrum discreteness.

## Contribution

The novel contribution is the design and fabrication of a continuous surface optical field modulator using random micro-cylindrical lens arrays.

## Key findings

- Random micro-cylindrical lens arrays can generate a small-angle Gaussian optical field to compensate for angular spectrum discreteness.
- The modulator achieved an angle error of less than 0.02° and a balance better than 0.5%.
- Surface structural roughness was measured to be below 10 nm.

## Abstract

The light homogenizing element is a crucial component of the illumination system of the lithography machine. Its primary purpose is to realize the uniform distribution of energy. However, it suffers from a common issue, which is angular spectrum discreteness, which significantly impacts light uniformity. To address this, we design and fabricate random micro-cylindrical lens arrays to obtain a small-angle Gaussian optical field, which can compensate for the angular spectrum discreteness. By adjusting the pitches and curvature radii of the micro-cylindrical lenses separately, we are able to manipulate the divergence angle of the emitted sub-beams, enabling precise angular spectrum modulation. By using mask-moving technology, the angular spectrum modulator is fabricated to generate a Gaussian illumination field. The surface profile is measured and determined with a structural roughness below 10 nm. Furthermore, optical test experiments on the modulator have been conducted, achieving an angle error of less than 0.02° and a balance better than 0.5%.