Extreme UV secondary electron yield measurements of Ru, Sn, and Hf oxide thin films

Jacobus M Sturm,Fred Bijkerk,Erik Darlatt,Christopher J Lee,Antonius A I Aarnink,Feng Liu,Michael Kolbe

doi:10.1117/1.jmm.18.3.033501

Abstract

Background: The secondary electron yield (SEY) of materials is important for topics as nanoparticle photoresists and extreme ultraviolet (EUV) optics contamination. Aim: Experimentally measure SEY and secondary electron energy distributions for Ru, Sn, and Hf oxide. Approach: The SEY and energy distribution resulting from 65 to 112 eV EUV radiation are measured for thin-film oxides or films with native oxide. Results: The total SEY can be explained by EUV absorption in the topmost nanometer of (native) oxide of the investigated materials. Conclusions: Although the relative SEY of Ru and Sn is well-explained by the difference in EUV absorption properties, the SEY of HfO2 is almost a factor 2 higher than expected. Based on the energy distribution of secondary electrons, this may be related to a lower barrier for secondary electron emission.

Highlights

Irradiation of materials with energetic photons, ions, or electrons results in generation of secondary electron emission from the surface
Quantitative measurements of secondary electron yields (SEYs) induced by extreme ultraviolet (EUV) radiation were performed on EUV mirrors and thin films of protective coating materials, most notably Ru, in order to understand the role of secondary electrons in EUV-induced contamination processes.[6]
This study shows that the SEY of materials may be, along with EUV absorption, an important factor for the sensitivity of EUV photoresists

Summary

Introduction

Irradiation of materials with energetic photons, ions, or electrons results in generation of secondary electron emission from the surface. It is often assumed that secondary electrons play a much more important role in driving chemical reactions as compared to direct photoabsorption processes.[5] Quantitative measurements of secondary electron yields (SEYs) induced by EUV radiation were performed on EUV mirrors and thin films of protective coating materials, most notably Ru, in order to understand the role of secondary electrons in EUV-induced contamination processes.[6]. Approach: The SEY and energy distribution resulting from 65 to 112 eV EUV radiation are measured for thin-film oxides or films with native oxide. Results: The total SEY can be explained by EUV absorption in the topmost nanometer of (native) oxide of the investigated materials. Based on the energy distribution of secondary electrons, this may be related to a lower barrier for secondary electron emission

Objectives

Results

Conclusion