Patent ID: 6348288
Filing Date: 2002-02-19
Classification: G03F

Abstract:
A method of fabricating a phase-shifting photomask comprising:providing a photomask blank comprising a chromium layer overlying a substrate and a resist layer overlying said chromium layer; exposing said resist layer of said photomask blank to electron-beam energy and developing away said resist layer whereby a first resist pattern remains; etching away said chromium layer not covered by said first resist pattern and simultaneously etching into said substrate not covered by said resist pattern to a depth of {fraction (1/4+L )} of the wavelength in nanometers of an exposure tool in which said phase-shifting photomask is to be used whereby a substrate step is formed underlying said first resist pattern; thereafter ashing away a portion of said first resist pattern to leave a second resist pattern smaller than said first resist pattern and exposing portions of said chromium layer underlying said first resist pattern; etching away exposed said portions of said chromium layer not covered by said second resist pattern whereby portions of underlying said substrate step are exposed; and removing said second resist pattern to complete fabrication of said phase-shifting photomask.