Extreme ultraviolet photoemission of a tin-based photoresist

Yu Zhang,Sonia Castellanos,Fredrik O L Johansson,Erika Giangrisostomi,Andreas Lindblad,Olivier Lugier,Jarich Haitjema,Najmeh Sadegh,Ruslan Ovsyannikov,Albert M Brouwer,Elin Berggren

doi:10.1063/5.0047269

Abstract

Tin is a suitable element for inclusion in extreme ultraviolet photoresists because of its relatively high-absorption cross section at 92 eV. The electrons emitted after photon absorption are expected to generate secondary electrons in the solid film. In this way, several pathways lead to reactive species that cause a solubility switch. Here, we report the photoelectron spectra of tin oxo cage photoresists over the photon energy range 60–150 eV, and the relative yields of photoelectrons from the valence band of the resist, from the Sn 4d orbitals, and of inelastically scattered electrons. The experimental excitation spectra differ considerably from those predicted by commonly used database cross section values, and from the combined computed subshell spectra: the maximum efficiency of ionization of Sn 4d both in the photoresists and in Sn metal occurs near the industrially relevant EUV wavelength of 13.5 nm.

Highlights

We show that the highest yield of Sn 4d electrons in the photon energy range 60–150 eV occurs near the EUV energy of 92 eV, rather than near 60 eV, which is predicted by quantum chemical calculations of subshell ionization cross sections.[23]
Our experiments were performed at the PM4 beam line of BESSY II, using a VG Scienta angle resolved time-of-flight (ArTOF) electron analyzer.[28]
The dipole beamline is equipped with a chopper that assures that pulsed x-rays are supplied to the LowDosePESstation

Summary

Introduction

We report the photoelectron spectra of tin oxo cage photoresists over the photon energy range 60–150 eV, and the relative yields of photoelectrons from the valence band of the resist, from the Sn 4d orbitals, and of inelastically scattered electrons.

Results

Conclusion