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