Next, a layer of {HEAD ~ BPSG} is deposited and reflowed in a steam atmosphere to produce {TAIL ~ an approximately planar surface} 
Next , a layer of { HEAD ~ BPSG } is deposited and reflowed in a steam atmosphere to produce { TAIL ~ an approximately planar surface }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL