c) removing said {TAIL ~ one or more extractable materials} leaving {HEAD ~ a porous structure} comprising said one or more non extractable insulation materials to form said low dielectric constant insulation layer; and 
c ) removing said { TAIL ~ one or more extractable materials } leaving { HEAD ~ a porous structure } comprising said one or more non extractable insulation materials to form said low dielectric constant insulation layer ; and
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH