Amplitude and phase beam shaping for the highest sensitivity in side-wall angle detection

TL;DR

This paper explores how optimized beam shaping can improve the sensitivity of side-wall angle detection in optical metrology, outperforming plane wave illumination, though further vectorial analysis is needed.

Contribution

It introduces a mathematical optimization method for designing beams that enhance side-wall angle detection sensitivity in optical metrology.

Findings

Optimized beam shaping improves detection sensitivity over plane waves.

Sensitivity decreases with increasing slope angles but remains better than plane wave case.

Further extension to vectorial cases is necessary for comprehensive application.

Abstract

In optical metrology, grating-like structures are used as tools to evaluate the performance of lithographic techniques. In particular, several shape parameters characterize those structures. One of them, termed side-wall angle, suffers from a considerable high error estimation. Using mathematical optimization, we investigated whether a properly shaped beam could increase the ability to detect tiny changes of this angle. This paper describes the theoretical formulation used to calculate the optimized beam and compares its performance with the case of a plane wave. We found that the sensitivity decreases with increasing slope angles, but even so its trend is better than in the plane wave case. Still, such an optimization process needs to be extended to the more general vectorial case.