Pellicle for ArF excimer laser photolithography

Abstract

Abstract We have developed pellicle for ArF excimer laser lithography. Especially we have studied light resistivity against ArFexcimer laser. We have selected fluoropolymer for ArF pellicle material because of its high transmission against deep uvlight.Transmission of the pellicle film at wavelength A. 193nm is over 99.5% at peak value from sinusoidal transmissionspectrum. Lifetime of our pellicle film against the ArF excimer laser irradiation is estimated for total exposure energy70,000J/cm2. Number of 300mm wafer processed within the lifetime becomes 480,000 wafers from the total exposureenergy 70,000J/cm2.Degradation mechanism ofpellicle film caused by the ArF excimer laser irradiation has been investigated. The degradationmechanism is interpreted as following. Pellicle film is first etched from its surface by the ArF excimer laser irradiation.This etching ofthe pellicle film causes the film thickness reduction and roughens the surface of the pellicle film. Thus thetransmission is reduced. The pellicle film material, which is fluoropolymer, however, has not changed on chemical basis.Fluorination of the pellicle film material, i.e., fluoropolymer, has improved its light resistivity against ArF excimer laser.Further fluorination ofpellicle film material is expected to improve more its light resistivity against ArF excimer laser.Keywords: pellicle, ArF excimer laser, lithography, fluoropolymer, transmission, lifetime, fluorination