In situ ellipsometry study of atomic hydrogen etching of extreme ultraviolet induced carbon layers

• Published in: Applied surface science 2011-10, Vol.258 (1), p.7-12
• Main Authors: Chen, Juequan, Louis, Eric, Harmsen, Rob, Tsarfati, Tim, Wormeester, Herbert, van Kampen, Maarten, van Schaik, Willem, van de Kruijs, Robbert, Bijkerk, Fred
• Format: Article
• Language: English
• Subjects: Atomic hydrogen etching; Carbon; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Ellipsometry; Etching; EUV-induced carbon contamination; Evaporation; Exact sciences and technology; Extreme values; Hydrocarbons; Photolithography; Physics; Ultraviolet
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2011.07.121

► In situ spectroscopic ellipsometry was applied to investigate the etch rate of EUV-induced carbon. ► The high etch rate of the EUV-induced carbon is related to the large hydrogen content. ► A hydrogenating process precedes the removal of carbon by atomic hydrogen. ► Strongest temperature dependence of the etch rate observed on EUV-induced carbon. Atomic hydrogen based etching is generally considered an efficient method for the removal of carbon films resulting from photo-induced hydrocarbon dissociation, as occurs in extreme ultraviolet (EUV) photolithography environments. The etch rate of atomic hydrogen for three different kinds of carbon films was determined, namely for EUV-induced carbon, hot filament evaporated carbon and e-beam evaporated carbon. The etching process was monitored in situ by spectroscopic ellipsometry. The etch rate was found to depend on the type of carbon (polymer or graphite-like), on the layer thickness, and on the temperature. The EUV-induced carbon shows the highest etch rate, with a value of ∼0.2 nm/min at a sample temperature of 60 °C. The more graphite-like carbon layers showed an etch rate that was about 10 times lower at this temperature. An activation energy of 0.45 eV was found for etching of the EUV-induced carbon layer.