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