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