{HEAD ~ A plurality} of micro passageways that penetrate the first surface of the substrate from the second surface are formed by {TAIL ~ a porous silicon process} 
are formed by
{ HEAD ~ A plurality } of micro passageways that penetrate the first surface of the substrate from the second surface are formed by { TAIL ~ a porous silicon process }
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL