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