High performance fluoride optical coatings for DUV optics

In deep ultraviolet region that typical applications are used on the ArF wavelength, coated optics should meet stringent requirements of optical systems. To meet these requirements, systematical researches are carried out on fabrication and characterization methods of fluoride coatings. First, by optimizing of deposition processes, dense coatings with the refractive index of ~1.7 for LaF3 and ~1.4 for MgF2, together with extinction coefficients of ~2×10-4 on 193nm were realized. The transmission of AR coating for 193nm achieved by using optimized deposition techniques is 99.8%. Second, a method of designing shadowing masks was developed to solve the problem of correcting coating thickness distributions for complex DUV systems. By using the method, the thickness distribution error specification of 3% PV has been achieved on substrates with ~300mm diameters and large curvatures. Finally, the laser calorimetry method is used to evaluate the laser radiation stability of fluoride coatings. It is turned out that the damage coefficients of fluoride coatings, which are defined as the values of unrecoverable increase of the absorption during the laser irradiation process, are much lower than that of fused silica substrates. The above progresses could further support the realization of high performance DUV optical systems.

[1]  J. Earl Rudisill.  Design/deposition process tradeoffs for high-performance optical coatings in the DUV spectral region , 2004, SPIE Laser Damage.

[2]  Horst Schreiber,et al.  Nanoporous structure of a GdF(3) thin film evaluated by variable angle spectroscopic ellipsometry. , 2007, Applied optics.

[3]  Norbert Kaiser,et al.  Optical coatings for UV photolithography systems , 1996, Optical Systems Design.

[4]  Uniformity Masks Design Method Based on the Shadow Matrix for Coating Materials with Different Condensation Characteristics , 2013, TheScientificWorldJournal.

[5]  Cheng-Chung Lee,et al.  Microstructure-related properties at 193 nm of MgF2 and GdF3 films deposited by a resistive-heating boat. , 2006, Applied optics.

[6]  S. Bublitz,et al.  Nonlinear absorption in single LaF(3) and MgF(2) layers at 193 nm measured by surface sensitive laser induced deflection technique. , 2009, Applied optics.

[7]  P. Baumeister,et al.  Optical interference coatings. , 1970, Applied optics.

[8]  D. Ristau,et al.  Coated Optics for DUV-Excimer Laser Applications. , 2000 .

[9]  O. Apel,et al.  Nonlinear absorption of thin Al2O3 films at 193 nm. , 2000, Applied optics.

[10]  Roland Thielsch,et al.  Optical Coatings for the DUV / VUV , 2003 .

[11]  D. Ristau,et al.  Impact of SiO2 and CaF2 surface composition on the absolute absorption at 193nm , 2011, Laser Damage.

[12]  Harro Hagedorn,et al.  Oxide and fluoride coatings for the excimer wavelength 193nm , 2005, SPIE Optical Systems Design.

[13]  Holger Blaschke,et al.  Absorptance measurements for the DUV spectral range by laser calorimetry , 2003, SPIE Laser Damage.

[14]  Hartmut Enkisch,et al.  Coatings for next generation lithography , 2008, Optical Systems Design.

[15]  Cheng-chung Lee,et al.  Microstructure related properties of lanthanum fluoride films deposited by molybdenum boat evaporation at 193 nm , 2005 .

[16]  Bincheng Li,et al.  Theoretical design of shadowing masks for uniform coatings on spherical substrates in planetary rotation systems. , 2012, Optics express.

[17]  David H. Peterson,et al.  Deposition and characterization of challenging DUV coatings , 2008, Optical Engineering + Applications.

[18]  Cheng-Chung Lee,et al.  Characterization of AlF3 thin films at 193 nm by thermal evaporation. , 2005, Applied optics.

[19]  Christian Muhlig,et al.  Simultaneous measurement of bulk absorption and fluorescence in fused silica upon ArF laser irradiation , 2002, SPIE Optics + Photonics.

[20]  Angela Duparré,et al.  Ultraviolet optical and microstructural properties of MgF2 and LaF3 coatings deposited by ion-beam sputtering and boat and electron-beam evaporation. , 2002, Applied optics.

[21]  K. Nishimoto,et al.  Fluoride antireflection coatings for deep ultraviolet optics deposited by ion-beam sputtering. , 2006, Applied optics.