Patent ID: 6914444

Claim:
An apparatus to test first and second areas of, on or in a semiconductor wafer wherein the first and second areas each include a pattern having a plurality of via or contact holes, the apparatus comprising: an electron beam source, adapted to irradiate an electron beam on the pattern of the first area and pattern of the second area; a current measuring device, adapted to measure an amount of current at a back surface of the wafer, wherein the current measuring device measures (i) a current in response to the electron beam source irradiating the pattern of the first area and (ii) a current in response to the electron beam source irradiating the pattern of the second area; and a defect detection device to detect a defect in at least one of the patterns of the first area and second area using (i) the amount of current measured in response to the electron beam source irradiating the pattern of the first area and (ii) the amount of current measured in response to the electron beam source irradiating the pattern of the second area.