PHOTO MASK BLANK, PHOTO MASK, AND THEIR FABRICATION METHOD

摘要

On one main surface of a transparent substrate (11) such as quartz as a photo mask substrate, a light shielding film (12) is arranged for exposure light. The light shielding film (12) is a so-called "light shielding film" and may also serve as a reflection preventing film. Moreover, the light shielding film has a film thickness not greater than 100 nm and is designed so that a film thickness of chrome-based compound having an optical density (OD) per unit film thickness for light having a wavelength of 450 nm is 0.025 nm^-1 occupies 70% of the entire film thickness or above. When this photo mask blank is used for fabricating a mask for ArF exposure, the film thickness and composition are selected so that the optical density of the light shielding film (12) is within a range from 1.2 to 2.3 for the light having a wavelength of 193 nm or 248 nm.