Preferably the ARC mask consists of a first layer of between 300 and 1500 angstroms of silicon rich silicon nitride having an extinction coefficient of from 0.77 to 1.07, and a second layer of {HEAD ~ between 170 and 320 angstroms} of {TAIL ~ silicon oxynitride} having an extinction coefficient of about 0.32 
Preferably the ARC mask consists of a first layer of between 300 and 1500 angstroms of silicon rich silicon nitride having an extinction coefficient of from 0.77 to 1.07 , and a second layer of { HEAD ~ between 170 and 320 angstroms } of { TAIL ~ silicon oxynitride } having an extinction coefficient of about 0.32
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