Characteristic diffuse scattering from distinct line roughnesses

TL;DR

This paper demonstrates that EUV small-angle scattering can distinctly characterize different types of line roughness in lamellar gratings, enabling rapid in-line nanostructure assessment.

Contribution

It introduces a method to differentiate line edge and line width roughness in lamellar gratings using EUV scatterometry, based on unique scattering patterns.

Findings

Distinct scattering patterns correlate with roughness types

EUV scatterometry enables rapid, in-line nanostructure characterization

Study validates the method with nine well-defined gratings

Abstract

Lamellar gratings are widely used diffractive optical elements; gratings etched into Si can be used as structural elements or prototypes of structural elements in integrated electronic circuits. For the control of the lithographic manufacturing process, a rapid in-line characterization of nanostructures is indispensable. Numerous studies on the determination of regular geometry parameters of lamellar gratings from optical and extreme ultraviolet (EUV) scattering highlight the impact of roughness on the optical performance as well as on the reconstruction of these structures. Thus, a set of nine lamellar Si gratings with a well defined line edge roughness or line width roughness were designed. The investigation of these structures using EUV small-angle scattering reveals a strong correlation between the type of line roughness and the angular scattering distribution. These distinct scattering patterns open new paths for the unequivocal characterization of such structures by EUV scatterometry.