Amorphous Refractory Compound Film Material for X-Ray Mask Absorbers

We proposed that the stress of the side walls of an absorber pattern causes the pattern distortion of an X-ray mask. The surfaces of the pattern side walls have a high compressive stress layer because they are easily oxidized in air after absorber pattern etching. This stress becomes a serious problem in proportion to the high degree of pattern integration. To lower the surface oxide layer stress of the film, we developed a TaGe nitride (TaGeN) absorber. The oxide layer stress of TaGeN films becomes lower with increasing the N2 content in the sputtering gas, and the stress value of Ta0.35Ge0.20N0.45 can be decreased to 1/17 that of TaGe. We fabricated a TaGeN X-ray mask and practically demonstrated that the TaGeN absorber was effective for high image placement accuracy to an X-ray mask having high dense patterns with a 0.1 µm pattern size.