Patent ID: 7754502

Claim:
A backside defect detector comprising: an IR receiver to detect an IR light beam at a plurality of locations on a semiconductor wafer, and measure an intensity of the IR light beam to generate a measured intensity for each of the plurality of locations; a memory to hold a plurality of stored intensities so that a stored intensity is held for each of the plurality of locations; and a controller connected to the IR receiver and the memory, the controller to determine a difference between the measured intensity and the stored intensity for each of the plurality of locations, determine if the difference at any location exceeds an error tolerance, indicate that a material permanently connected to a top side of the semiconductor wafer has been completely removed from a bottom side of the semiconductor wafer when the difference at all locations is below the error tolerance, and indicate that the material remains on the bottom side of the semiconductor wafer when the difference at any location exceeds the error tolerance.