Ikuo Sakurai

Pellicle for ArF excimer laser photolithography

We have developed pellicle for ArF excimer laser lithography. Especially we have studied light resistivity against ArF excimer laser. We have selected fluoropolymer for ArF pellicle material because of its high transmission against deep uv light. Transmission of the pellicle film at wavelength (lambda) equals 193 nm is over 99.5% at peak value from sinusoidal transmission spectrum. Lifetime of our pellicle film against the ArF excimer laser irradiation is estimated for total exposure energy 70,000 J/cm2. Number of (phi) 300 mm wafer processed within the lifetime becomes 480,000 wafers from the total exposure energy 70,000 J/cm2. Degradation mechanism of pellicle film caused by the ArF excimer laser irradiation has been investigated. The degradation mechanism is interpreted as following. Pellicle film is first etched from its surface by the ArF excimer laser irradiation. This etching of the pellicle film causes the film thickness reduction and roughens the surface of the pellicle film. Thus the transmission 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 of pellicle film material is expected to improve more its light resistivity against ArF excimer laser.