# Grazing Incidence Small Angle X-Ray Scattering (GISAXS) on Small Targets Using Large Beams

## TL;DR

This paper demonstrates a method to adapt GISAXS for small, isolated targets on structured surfaces by using large beams and orientation techniques, enabling applications in semiconductor metrology.

## Contribution

The paper introduces a novel approach to separate target signals from surrounding structures in GISAXS measurements using target orientation, expanding its applicability to small and complex samples.

## Key findings

- Successful separation of target and surrounding scattering signals.
- Effective measurement of small targets down to 4 μm line length.
- Technique applicable for semiconductor metrology fields.

## Abstract

GISAXS is often used as a versatile tool for the contactless and destruction-free investigation of nanostructured surfaces. However, due to the shallow incidence angles, the footprint of the X-ray beam is significantly elongated, limiting GISAXS to samples with typical target lengths of several millimetres. For many potential applications, the production of large target areas is impractical, and the targets are surrounded by structured areas. Because the beam footprint is larger than the targets, the surrounding structures contribute parasitic scattering, burying the target signal. In this paper, GISAXS measurements of isolated as well as surrounded grating targets in Si substrates with line lengths from $50\,{\rm\mu m}$ down to $4\,{\rm\mu m}$ are presented. For the isolated grating targets, the changes in the scattering patterns due to the reduced target length are explained. For the surrounded grating targets, the scattering signal of a $15\,{\rm\mu m}\,\times\,15\,{\rm\mu m}$ target grating structure is separated from the scattering signal of $100\,{\rm\mu m}\,\times\,100\,{\rm\mu m}$ nanostructured surroundings by producing the target with a different orientation with respect to the predominant direction of the surrounding structures. The described technique allows to apply GISAXS, e.g. for characterization of metrology fields in the semiconductor industry, where up to now it has been considered impossible to use this method due to the large beam footprint.