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