Evolution of Secondary Electrons Emission During EUV Exposure in Photoresists

Abstract

Low energy electronic processes are key to chemical reactions during exposure of photoresists in extreme ultraviolet lithography. To understand and optimize the functionality of photoresists, it is of paramount important to assess the magnitude of the electron distribution inside the material. While photoemission spectroscopy is being widely used, vacuum barrier crossing and nonideal photoemissivity alter the measured spectra in a way that prevents meaningful assessment of very low energy electrons. In this work we propose a model to account for the physics of photoemission effects and to reliably estimate the distribution from solid state matter. The model also provides a quantitative value for the occupation function and density of state. We tested the model on the photoemission spectra acquired on a prototype EUV photoresist and report here the results.