Next, the windows are etched through {HEAD ~ the silicon nitride} with {TAIL ~ CH3 F or O2 /CHF3 gases} 
Next , the windows are etched through { HEAD ~ the silicon nitride } with { TAIL ~ CH3 F or O2 /CHF3 gases }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL