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