“The expression ion sputtering {TAIL ~ component} contained in {HEAD ~ an etching gas}” means, for example, Ar gas in the conventionally used etching gas  
“ The expression ion sputtering { TAIL ~ component } contained in { HEAD ~ an etching gas } ” means , for example , Ar gas in the conventionally used etching gas
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH