Attenuated phase shift mask

摘要

An attenuated phase shift mask comprises a first layer having a thickness to provide a transmission in the range of about 3 to 10% formed on a transparent substrate and a second layer comprising a transparent material having a thickness to provide a desired phase shift, formed on said first layer. For a phase shift of 180 DEG and i-line wavelength (365 nm) where chromium is used as the first layer, then a thickness within the range of about 25 to 75 nm is employed; where silicon dioxide is used as the second layer; then a thickness of about 400 to 450 nm is employed. While the oxide may be dry-etched, an isotropic wet etch provides superior aerial images.