The term etching factor refers to {HEAD ~ the ratio} of etching depth with {TAIL ~ respect} to the amount of side etching 
with
The term etching factor refers to { HEAD ~ the ratio } of etching depth with { TAIL ~ respect } to the amount of side etching
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH