Study on EUV photomask resist stripping and cleaning

Abstract

Any cleaning technology for state-of-the-art photo masks requires that pattern damage does not occur and optical characteristics do not change. Particularly with EUV masks, an important challenge is to suppress/prevent changes to the optical characteristics of ruthenium (Ru) film that generates when resist is removed (separated).This report illustrates a model explaining why optical characteristics change when conventional resist removal (separation) technologies are used on EUV mask. It also proposes a new resist removal technology that allows resist to be removed without any optical damage to Ru films.