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