After being bonded to the device wafer , the cap wafer is thinned from the back surface until {HEAD ~ the back surface} of {TAIL ~ the cap wafer} reaches the partially etched cavities  
of
After being bonded to the device wafer , the cap wafer is thinned from the back surface until { HEAD ~ the back surface } of { TAIL ~ the cap wafer } reaches the partially etched cavities
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH