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