Preferably {HEAD ~ the ARC mask} consists of {TAIL ~ 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 between 170 and 320 angstroms of silicon oxynitride having an extinction coefficient of about 0.32 
consists of
Preferably { HEAD ~ the ARC mask } consists of { TAIL ~ 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 between 170 and 320 angstroms of silicon oxynitride having an extinction coefficient of about 0.32
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH