{TAIL ~ The windows} are etched through {HEAD ~ the glass layer} with BCl2 or CHF3 /CF4 etch gases 
{ TAIL ~ The windows } are etched through { HEAD ~ the glass layer } with BCl2 or CHF3 /CF4 etch gases
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH