{HEAD ~ The substrate} is etched using {TAIL ~ reactive ion etching}, creating a coil shaped trench in the substrate 
is etched using
{ HEAD ~ The substrate } is etched using { TAIL ~ reactive ion etching } , creating a coil shaped trench in the substrate
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH