SUBSTRATE OBSERVING DEVICE AND SUBSTRATE POLISHING DEVICE

PROBLEM TO BE SOLVED: To provide a substrate observing device, can suppress the drift generated at the phase detection processing due to the integral multiple order of the high harmonic of reference signal. SOLUTION: A substrate observing device 31 includes: a reference signal source 61 outputting rectangular wave reference signal; a first filter circuit 63 for converting the rectangular wave from the reference signal source to sine wave; an excitation part 41 outputting the sine wave passed through the first filter circuit to the substrate; a detection part 43 receiving the detection signal from the substrate; a phase detection circuit 77 multiplying the reference signal by the detection signal from the substrate; a second filter circuit 79 connected to the latter stage of the phase polishing circuit; and a third filter circuit 73, set between the detection part 43 and the phase detection circuit 77, eliminating the integral multiple order of the higher harmonics of the reference signal from the detection signal. For the third filter circuit 73, the third order higher harmonics of the reference signal may be eliminated. COPYRIGHT: (C)2010,JPO&INPIT