Quantitative Chemically-Specific Coherent Diffractive Imaging of Buried Interfaces using a Tabletop EUV Nanoscope

TL;DR

This paper demonstrates a non-invasive, high-resolution EUV coherent diffractive imaging technique using a tabletop setup to visualize and analyze buried interfaces and material changes in nanostructures with chemical specificity.

Contribution

It introduces a tabletop EUV CDI method capable of quantitatively imaging buried interfaces and detecting material evolution with chemical specificity, surpassing existing techniques.

Findings

High-contrast imaging of buried structures through aluminum coating.

Detection of interstitial diffusion and oxidation layers at interfaces.

Quantitative, chemically-specific imaging of buried interfaces.

Abstract

Characterizing buried layers and interfaces is critical for a host of applications in nanoscience and nano-manufacturing. Here we demonstrate non-invasive, non-destructive imaging of buried interfaces using a tabletop, extreme ultraviolet (EUV), coherent diffractive imaging (CDI) nanoscope. Copper nanostructures inlaid in SiO2 are coated with 100 nm of aluminum, which is opaque to visible light and thick enough that neither optical microscopy nor atomic force microscopy can image the buried interfaces. Short wavelength (29 nm) high harmonic light can penetrate the aluminum layer, yielding high-contrast images of the buried structures. Moreover, differences in the absolute reflectivity of the interfaces before and after coating reveal the formation of interstitial diffusion and oxidation layers at the Al-Cu and Al-SiO2 boundaries. Finally, we show that EUV CDI provides a unique capability for quantitative, chemically-specific imaging of buried structures, and the material evolution that occurs at these buried interfaces, compared with all other approaches.