title: Development of optical coatings for 157-nm lithography. I. Coating materials.
abstract: In a basic study to identify low-loss optics for applications in F2 lithography, five potential coating materials (AlF3, Na3AlF6, MgF2, LaF8, and GdF3) and three deposition methods (thermal evaporation by a resistance heater and by electron beam and ion-beam sputtering) were investigated in the vacuum ultraviolet (VUV) region. Samples were supplied as single-layer coatings on CaF2 substrates by four Japanese coating suppliers. Refractive indices (n) and extinction coefficients (k) of these coatings at 157 nm were evaluated; the transmittance and the reflectance were measured by a VUV spectrometer and were compared. As a result, resistance heating thermal evaporation is seen to be the optimal method for achieving low-loss antireflection coatings. The relation among optical constants, microstructures, and stoichiometry is discussed.
authors.affiliation: Association of Super-Advanced Electronics Technologies (ASET), Hiratsuka Kanagawa, Japan. shunsuke.neu@nikon.co.jp
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Niisaka
authors.forename: Tadahiko
authors.initials: T
authors.lastname: Saito
authors.forename: Jun
authors.initials: J
authors.lastname: Saito
authors.forename: Akira
authors.initials: A
authors.lastname: Tanaka
authors.forename: Akira
authors.initials: A
authors.lastname: Matsumoto
authors.forename: Minoru
authors.initials: M
authors.lastname: Otani
authors.forename: Ryuji
authors.initials: R
authors.lastname: Biro
authors.forename: Chidane
authors.initials: C
authors.lastname: Ouchi
authors.forename: Masanobu
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Kazuho
authors.initials: K
authors.lastname: Sone