Stabilization of ZrSixOy Films by Irradiation with an ArF Excimer Laser

ZrSixOy is a candidate material for fabricating attenuated phase-shift masks used in ArF excimer laser lithography. To investigate the durability mechanism of ZrSixOy films following irradiation with an ArF excimer laser, we analyzed the films chemically and physically. The phase shift and the transmittance of a transmissive film with a high oxygen concentration increases and decreases, respectively, with irradiation. This is because of an increase of Si-O-Zr bond structures. The phase shift and the transmittance of an absorptive film with a low oxygen concentration decreases and increases, respectively, with irradiation because of photooxidation at the surface. The oxidation leads to the formation of Si-O-Zr and Si-O-Si bond structures in the films. Both films are stabilized by irradiation with a large irradiation energy. We interpret that both films are stabilized by the formation of Si-O-Zr bond structures, such as zircon, with saturation of oxygen concentrations at the surface.