Process to fabricate a double layer attenuated phase shift mask (apsm)

Abstract

A new process for fabricating an attenuated phase-shifting photomask is described. A photomask blank is provided comprising a phase-shifting layer overlying a substrate, a chromium layer overlying the phase-shifting layer, and a resist layer overlying the chromium layer. The resist layer of the photomask blank is exposed to electron-beam energy wherein a main pattern area of the photomask blank is exposed to a first dosage of the electron-beam energy and wherein a border area surrounding the main pattern area is not exposed to the electron-beam energy and wherein a secondary pattern area between the main pattern area and the border area is exposed to a second dosage of electron-beam energy wherein the second dosage is lower than the first dosage. The exposed resist layer is developed wherein the resist within the main pattern area is removed to expose the chromium layer. The exposed chromium layer is etched through to expose the underlying phase-shifting layer. The exposed phase-shifting layer is etched through to expose the substrate. The resist overlying the chromium layer within the secondary pattern area is etched away. The chromium layer within the secondary pattern area is etched away. The resist within the border area is stripped away to leave a patterned phase-shifting layer in the main pattern area and a chromium layer in the border area to complete fabrication of the attenuated phase-shifting photomask.