Research And Fabrication Of Antireflection (AR) Coatings For P-polarized ArF Excimer Laser Light At Big Incidence Angle

ArF excimer lasers have been increasingly applied in semiconductor exposure,material microstructuring and medical surgeries because of its high power, highhomogeneity and high stability. The ArF excimer lasers are keeping developed forhigher output power and frequency. Especially in the semiconductor exposure area,the193nm ArF lithography system is one of the most complicated systems that menhave built. Especially in the semiconductor industry, the193nm ArF lithographytechnology is extending for higher resolution node, which makes an ever-growingdemand on the performance and stability of the coating components inside the system.Line narrowing module (LNM) with high precision is needed to obtain extremenarrow bandwidth of wavelength in the ArF excimer laser cavity, contains severalprisms for beam expanding. In order to obtain enough expanding ratio, the incidenceangle of P-polarized193nm laser beam on the hypotenuse of the expanding prisms areusually selected between68o-75°. Because of the large angle of incidence, it couldcause severe reflection losses using uncoated expanding prisms. So the hypotenusesurfaces of the expanding prisms are needed to be coated with antireflection (AR)coatings for P-polarized light to reduce the reflection loss.The characteristic of P-pol light oblique incident on thin film systems is analyzed in theory.The needle optimize arithmetic is applied for the coating design based on themain technique difficulty of AR coatings for P-polarized ArF laser at large angle ofincidence, and the error influence of the optimum design is evaluated.The optimization of depositing process for AR coatings for P-polarized ArF laserat large angle of incidence is discussed in detail, including the chosen andcharacterization of surper polished substrates, the effect of process parameters on thedepositing materials characteristic.The correlative performance of AR coatings for P-polarized laser beam at largeangle of incidence were tested and evaluated, including the optical performance suchas residual reflection, transimission and angle tolerance and etc. The absorptance andscattering losses, the stability against laser radiation and time were assessed, whichproviding a comprehensive evaluation of the AR coatings for P-polarized ArF laser atlarge angle of incidence.The AR coatings for P-polarized ArF laser at angle of incidence equal71oand74owere obtained for the first time in China, whose quality could match the productsprovided by the first-class optical coating companies like Acton in USA, Sigma inJapan and etc.