EUV-induced oxidation of thin CrO films on SiN free-standing windows

Description

The physics of the interaction of matter with soft X-ray and extreme ultraviolet (EUV) is complicated, EUV photons break chemical bonds, generate secondary electron cascades and create radicals in the background gas. To study these intertwined processes, chromium oxide (CrOx) cap layers (3-5 nm) on SiN free-standing windows are exposed to EUV in a vacuum, hydrogen and water background using the BESSY II synchrotron. To exclude reoxidation in air, the novel technique of in-vacuo EUV transmission (EUVT) measurements is used.

The EUVT is stable in vacuum and hydrogen exposure conditions, indicating that CrOx is stable in solely EUV. However, in increased water background the EUVT decreased, which is typically explained by oxygen absorption increasing EUV absorption (EUVA). Contrary to expectations, the EUVA (determined ex-situ) did not increase, instead, the EUV reflection increased, indicating a change in optical constants.

X-ray photoelectron spectroscopy (XPS) revealed a SiNO2 peak in the EUV + water exposure and not in EUV + hydrogen. But the EUVA in water did not increase. Therefore, EUV metrology and XPS contributed to modelling the complex physics of EUV interaction with matter.

Period	14 Oct 2025
Event title	8th PTB-Seminar on VUV and EUV Metrology 2025
Event type	Seminar
Conference number	8
Sponsors	OptiX fab GmbH, Carl Zeiss Jena
Location	Berlin, Germany, BerlinShow on map
Degree of Recognition	International