SCANNING PHOTON MICROSCOPE

摘要

PURPOSE:To improve the sensitivity of the detection of a contaminated part on the surface of a semiconductor wafer or a defective which is present locally by performing the synchronous phase detection of an AC light voltage in the semiconductor wafer surface and subtracting a DC component contained in the distribution of a light voltage with an effective value. CONSTITUTION:When light which becomes intermittent light of frequency through brightness modulation is projected on the semiconductor wafer 14, the AC light voltage is generated. This voltage can be detected by the electrostatic capacity consisting of the wafer 14 and a transparent electrode 15 without forming any electrode on the wafer 14. The detected AC light voltage is controlled to the effective value of the AC voltage of a synchronous phase detector 24 and inputted to a signal processing circuit 6. The signal after the contrast is emphasized by this circuit 6 is A/D-converted 7 and stored in a frame memory 9 through the interface circuit 8 of a microcomputer 12. The light spot of a CRT 18, on the other hand, is scanned at a spot position by the deflecting coil 19 of a deflection driving circuit 21 according to a signal from an oscillator 23. Consequently, information in the plane of a wafer 14 is stored in a memory 9 and this information is displayed 11 through a scan converter 10 to obtain a light voltage distribution image.