Eddy current sensor

摘要

An eddy current sensor ( 10 ) has a sensor coil ( 100 ) disposed near a conductive film ( 6 ) formed on a semiconductor wafer (W) and a signal source ( 124 ) configured to supply an AC signal to the sensor coil ( 100 ) to produce an eddy current in the conductive film ( 6 ). The eddy current sensor ( 10 ) includes a detection circuit operable to detect the eddy current produced in the conductive film ( 6 ). The detection circuit is connected to the sensor coil ( 100 ). The eddy current sensor ( 10 ) also includes a housing ( 200 ) made of a material having a high magnetic permeability. The housing ( 200 ) accommodates the sensor coil ( 100 ) therein. The housing ( 200 ) is configured so that the sensor coil ( 100 ) forms a path of a magnetic flux (MF) so as to effectively produce an eddy current in the conductive film ( 6 ).