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