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