MONITOR FOR CHANGE IN THICKNESS

PROBLEM TO BE SOLVED: To monitor the change in film thickness on the spot by inducing an eddy current in a film, monitoring current which changes as the thickness of the film changes, and eliminating a metal film from a semiconductor substrate. SOLUTION: A meted film 100 is formed on one surface of a wafer 102. A sensor 110 which has a circuit consisting of a capacitor 118 and a coil 114 wound around a ferrite toroid 112 is wound around the rear surface of the wafer 102. When the sensor 110 is excited by the sweeping output of a spectrum analyzer 130 via a resistor 120, a vibration current flows through the coil 114 and an eddy current is induced in the film 100 due to an alternate electromagnetic field. A sensor spectrum detected by the analyzer 130 has a resonance peak at a specific frequency related to a tank circuit and the film 100 being monitored. Then, the change in the film thickness can be monitored according to the change in peak amplitude, width, and resonance frequency due to the elimination of the film 100.