Optimal decentralized wavelength control in light sources for lithography

TL;DR

This paper develops a decentralized LQG framework for optimal wavelength control in pulsed light sources used in lithography, effectively compensating delays and outperforming existing methods.

Contribution

It introduces a novel decentralized control approach for wavelength regulation in light sources, addressing delays and cooperative interactions among optics modules.

Findings

Exact compensation of measurement and time-delays achieved

Optimal controller outperforms existing wavelength control techniques

Framework applicable to multi-optics modules in lithography

Abstract

Pulsed light sources are a critical component of modern lithography, with fine light beam wavelength control paramount for wafer etching accuracy. We study optimal wavelength control by casting it as a decentralized linear quadratic Gaussian (LQG) problem in presence of time-delays. In particular, we consider the multi-optics module (optics and actuators) used for generating the requisite wavelength in light sources as cooperatively interacting systems defined over a directed acyclic graph (DAG). We show that any measurement and other continuous time-delays can be exactly compensated, and the resulting optimal controller implementation at the individual optics-level outperforms any existing wavelength control techniques.