Performance optimization of 193 nm antireflective coatings with wide incident angle ranges on strongly curved spherical substrates.

Abstract

A method to optimize the spectral performance of 193 nm antireflective (AR) coating with a broad range of angle of incidence (AOI) on strongly curved spherical substrates is described. In this method, the actual film thickness on test plates for single-layer LaF3 and MgF2 films are corrected by measuring the relationship between the film thickness on test plates and that on quartz crystal microbalance. Interface roughness in multi-layer AR coating is obtained from atomic force microscopy measurements and its effect on the spectrum of the multi-layer is taken into account in this method by being simulated as a homogeneous sublayer. Porosities of the sublayers in AR coatings are obtained by reversely engineering the residual reflectance of the coatings/substrate/coating stacks. The obtained refractive indices and thicknesses in the multilayer are then used for analysis and optimization of the spectrum of 193 nm AR coatings. For strongly curved spherical surfaces, spectrum uniformity of the AR coating is optimized by taking into consideration simultaneously the merit functions at different positions of spherical substrates. This work provides a general solution to the performance optimization of 193 nm AR coatings with broad AOI range and on strongly curved spherical substrates.