Typically, the first group of {TAIL ~ semiconductor wafers} have impurities therein which are to be removed and the second group of semiconductor wafers are to receive {HEAD ~ the impurities} 
Typically , the first group of { TAIL ~ semiconductor wafers } have impurities therein which are to be removed and the second group of semiconductor wafers are to receive { HEAD ~ the impurities }
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD