Calibration-based overlay sensing with minimal-footprint targets

TL;DR

This paper introduces a calibration-based overlay sensing method using minimal-footprint targets with scattering nanoparticles, enabling precise overlay measurements in semiconductor fabrication with fewer and smaller targets.

Contribution

It presents a novel approach to overlay measurement using tiny nanoparticle-based targets and demonstrates calibration transferability across instances.

Findings

Successful readout of overlay errors using small nanoparticle targets

Calibration on one target realization applies to subsequent measurements

Finer sampling of deformation improves overlay measurement accuracy

Abstract

Overlay measurements are a critical part of modern semiconductor fabrication, but overlay targets have not scaled down in the way devices have. In this work, we produce overlay targets with very small footprint, consisting of just a few scattering nanoparticles in two separate device layers. Using moir\'e patterns to deterministically generate many overlay errors on a single chip, we demonstrate successful readout of the relative displacement between the two layers and show that calibration on one realization of the targets can be used for overlay measurements on subsequent instances. Our results suggest using greater quantities of smaller overlay targets may benefit performance both directly and through finer sampling of deformation.