Spectrum Uniformity Optimizaion Of 193nm AR Coatings On Spherical Substrates

Photolithography systems working at 193nm,with the technical node ranging from130 nm to 22 nm,have been an industrial workhorse for manufacturing advanced intergrated circuit components.Antireflective?AR?coating is a crucial process in fabricating 193 nm optical photolighography systems.Firstly,the requirements in overall throughtput and transmission uniformity at the pupil of the system translate into strick requirements in film thickness uniformity and optical losses ofAR coatings on each surface of the systems.Secondly,some of the lenes are designed into large clear aperture with very steep surfaces and wide range of angle of incidence to achieve high numerical aperature.Thicknesses,structural and optical properties of fluoride films over the steep surfaces are strongly related to the positions on the substrate.This work aims to provide method to improve the film thickness and spectrum uniformity of 193 nm AR coatings on such steep spherical substrates.For the purpose,coating processes,film thickness uniformity and design of 193nm antireflective on steep spherical surfaces of a photo-lithography system with number aperature 0.75 are investigated.Firstly,techniques to improve the film thickness unfiormtiy of single fluoride films on spherical substrates are explored.From the relationship between film thickness distribution before correction and the expanding angles of shadowing masks,we reveal that film thickness distribution can be theorecially improved by increase the size of planar shadowing masks.Morevoer,we revealed that film thickness distribution on spherical substrate is influenced by non-linear dependence of deposition rate on cosine function of moluecular injection angle.After taking into this effect into consideration,accordance between theoretical simulation and experimental results are improved greatly.Secondly,structural and optical properties of single LaF₃ and MgF₂ films on spherical substrate are investigated.We reveal that comular angles of the films increase from the center to the rim of a spherical substrate and analyz the distribution of comular angles on the substrate with flux vector theory.Accompanied by the increase of comular angles,refractive index inhomogeneity increases from the center to the rim of the substrate.Thirdly,design of fluoride AR coating is investigated.The effects of thickness error,interface roughness,and refractive index inhomogeneity on spectrum of AR coatings are demonstrated.Only by taking these effects into consideration during multi-parameter optimization process,will the spectra from theoretical design accord well with experimental result.With the same method,performance of AR coating on a steep spherical substrate is investigated.The spectrum uniformity of AR coatings can be improved by taking the performance of AR coating at different positions of spherical substrate into optimization simulatineously.In short,a deep research is carried out about the structural and optical properties,film thickness uniformity and spectrum uniformity of 193nm AR coatings on spherical substrates.The results can be applied in AR coating for 193 nm lithography equipment with different numerical aperature and helpful for the development of 193nm lithography machine in China.