{HEAD ~ The first step} of the contact etch is accomplished using {TAIL ~ a boron trichloride BCL3 etch gas} which selectively etches BPSG without etching the underlying silicon nitride 
is accomplished using
{ HEAD ~ The first step } of the contact etch is accomplished using { TAIL ~ a boron trichloride BCL3 etch gas } which selectively etches BPSG without etching the underlying silicon nitride
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH