Investigating extreme ultraviolet radiation chemistry with first-principles quantum chemistry calculations

Jonathan H Ma,Han Wang,Patrick Naulleau,Andrew Neureuther,David Prendergast

doi:10.1117/1.jmm.19.3.034601

Abstract

In extreme ultraviolet (EUV) lithography, chemistry is driven by secondary electrons. A deeper understanding of these processes is needed. However, electron-driven processes are inherently difficult to experimentally characterize for EUV materials, impeding targeted material engineering. A computational framework is needed to provide information for rational material engineering and identification at a molecular level. We demonstrate that density functional theory calculations can fulfill this purpose. We first demonstrate that primary electron energy spectrum can be predicted accurately. Second, the dynamics of a photoacid generator upon excitation or electron attachment are studied with ab-initio molecular dynamics calculations. Third, we demonstrate that electron attachment affinity is a good predictor of reduction potential and dose to clear. The correlation between such calculations and experiments suggests that these methods can be applied to computationally screen and design molecular components of EUV material and speed up the development process.

Highlights

With the introduction of extreme ultraviolet (EUV), electron-driven processes in photoresists become relevant
7 Conclusion In summary, four electron processes in EUV exposure radiation chemistry were studied by density functional-based calculations
ab-initio molecular dynamics (AIMD) calculations were shown to reproduce the immediate outcome of internal excitation

Summary

Introduction

With the introduction of extreme ultraviolet (EUV), electron-driven processes in photoresists become relevant. In EUV, upon photon absorption, a high kinetic energy primary electron is very likely to be produced as a result. Such primary electrons are very unlikely to initiate chemistry immediately; instead, they rapidly lose energy through generating a cascade of low kinetic energy secondary electrons.[3] In the context of chemically amplified resists (CARs), the PAG can be activated through internal excitation[4] or low kinetic energy electron attachment,[3] which is hypothesized to be the main driver of EUV chemistry. All constituents of the photoresist participate in the photon-tochemistry conversion Understanding these electron processes is vital for several reasons. We report that electron attachment calculations can be applied to predict reduction potential and dose to clear

Ionization Calculations

Internal Excitation

Electron Attachment

Conclusion