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