Research On The High Reflection Coatings In ArF Excimer Laser

Integrated circuit (IC) manufacturing is one of the strategic industries to whichis given great attention in our country. With the continuous development oflithography technology, the density of integrated circuit has become higher, and thesize has become smaller. Since the end of the20th century, ArF excimer laserprojection lithography has become the mainstream equipment of90nm and65nmnode huge scale integrated circuit manufacturing. Therefore,193nm optical thin filmdevices which applied in ArF excimer laser and its corresponding optical systemhave played an important role. In this paper, the research and preparation have beencarried on the high reflection (HR) coatings which is used by193nm laser opticalsystem, the technical requirements of low loss and high damage threshold for opticalthin film components have been proposed. The main contents are as follows:1. In order to prepare the optical thin film components which meet theperformance requirements, you must accurately identify the optical constants(refractive index and extinction coefficient) of the thin film materials used in thecorresponding wavelength range. The optical constants of the materials in the thinfilm state and the block state vary greatly, and depend on the deposition methods.Under various specific preparation conditions, accurate analysis of thin film opticalconstants is one of the most important aspects of the preparation of highperformance film optical elements. According to LaF3film growth characteristicsprepared by thermal evaporation, this paper proposes a characterization of the refractive index inhomogeneity of thin film optical constants, which is based oninhomogeneous model and spectrophotometry method to determine the opticalconstants of thin film at the same time, and to do the mutual authentication with themethod of ellipsometry, and to improve the optical constants of analytic precisionwhen the thin film is in the deep ultraviolet wavelength range.2. The optical properties of thin film depend on the deposition methods andconditions, and the analysis on the thin film which prepared under differentdeposition conditions and process parameters are needed. Detailed study on theoptical properties and structure of LaF3, MgF2, GdF3and AlF3film that prepared bythermal evaporation under different deposition temperature and deposition rate, andsystematical characterization on optical properties, microstructure, chemicalcomposition and laser calorimetry of thin film. So as to determine the film propertiesunder various process parameters.3. Based on the distribution characteristics of electric field intensity in the bodyof HR coatings, the thin film has been optimized designed. According to the result ofdesign and optimization of deposition process, the193nm HR coatings has beenprepared, the thin film loss and error of inversion have been analyzed, and identifythe reasons of the error between the theoretical design and practical preparation, soas to improve the HR coatings deposition process.4. For the preparation193nm HR coatings, ArF excimer laser damage test hasbeen done, analyze the thin film’s damage morphology, systematically research thecorrelation between the thin film properties and its evolution and the coating damage.Starting from the two aspects of theory and experiment, deduce the ArF excimerlaser damage mechanism of fluoride HR coatings, increase the film laser induceddamage threshold from1.0J/cm2to2.25J/cm2on the basis of optimizing use ofsurface defects, packing density and coating design under1-on-1damage mode.