| 摘要 |
PURPOSE:To improve the detecting sensitivity of a photovoltage and the positional resolution by reducing the voltage detecting area of a transparent electrode as compared with the surface area of a sample wafer and constructing to move a wafer with respect to an optical beam. CONSTITUTION:In order to reduce the voltage detecting area, a transparent electrode 4' having a smaller electrode area than the surface area of the wafer such as the electrode 4' disposed in a range of 10mm. in diameter on a sample wafer 2 of 100mm. in diameter is arranged directly under an optical beam. A spacer 5' and a glass plate 6' are also reduced in the same manner as the electrode 4'. Accordingly, the voltage to be detected is detected largely in accordance with the area ratio (100mm.)<2>/(10mm.)<2>approx.=100. In order to further move the wafer 2, a Y- direction stage 11 is provided on a trestle 10, and an X-direction stage 12 is disposed on the stage 11. A turntable 12 is provided on the stage 12, and a vacuum chuck is placed on the table. Thus, the wafer 2 can be disposed at the arbitrary position with respect to the beam 1.
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