Characterization of secondary electron blur via determination of electron attenuation length

Abstract

The absorption of an EUV photon by a thin film resist leads to the emission of a photoelectron as well as several secondary electrons with low kinetic energy. The “universal curve”, used in X-ray photoelectron spectroscopy, indicates that the low kinetic energy electrons may travel tens to hundreds of nanometers before losing their kinetic energy via initiation of chemical reactions. The distance that the electrons are able to travel in the resist is directly related to the resultant “blur” of the aerial image. Thus, identifying how to measure and influence the distance traveled by the secondary electrons is extremely beneficial to the resist community. In this work, we utilize several model polymer materials to investigate the impact of specific chemistry groups on the secondary electron attenuation length (EAL) – the thickness of resist material required to reduce number of emitted secondary electrons to 1/e of initial. The EAL measures the distance the secondary electrons can travel in a resist film, which is directly related to the electron blur. Possibilities to gain additional information on electron penetration depth in resist films will also be discussed.