Differential electron yield imaging with STXM

TL;DR

This paper introduces differential electron yield (DEY) imaging with STXM, a new technique that maps device connectivity and distinguishes electrons and holes without needing electric fields, aiding failure analysis.

Contribution

The paper presents DEY-STXM, a novel imaging method that provides independent electron and hole sensitivity without electric fields, enhancing device failure analysis capabilities.

Findings

DEY-STXM can map device connectivity landscapes.

DEY contrast changes sign based on electrode connection.

Application demonstrated on a failed aluminum nanowire.

Abstract

Total electron yield (TEY) imaging is an established scanning transmission X-ray microscopy (STXM) technique that gives varying contrast based on a sample's geometry, elemental composition, and electrical conductivity. However, the TEY-STXM signal is determined solely by the electrons that the beam ejects from the sample. A related technique, X-ray beam-induced current (XBIC) imaging, is sensitive to electrons and holes independently, but requires electric fields in the sample. Here we report that multi-electrode devices can be wired to produce differential electron yield (DEY) contrast, which is also independently sensitive to electrons and holes, but does not require an electric field. Depending on whether the region illuminated by the focused STXM beam is better connected to one electrode or another, the DEY-STXM contrast changes sign. DEY-STXM images thus provide a vivid map of a device's connectivity landscape, which can be key to understanding device function and failure. To demonstrate an application in the area of failure analysis, we image a 100~nm, lithographically-defined aluminum nanowire that has failed after being stressed with a large current density.