| 摘要 |
PURPOSE:To allow highly accurate detection of a position and positioning regardless of the surface form of a sample by providing a means that has 2 slender slits parallel to the surface of the sample and irradiates an image so that the image of aligned parallel slits are projected and focused in the direction differing with respect to the direction of the circuit pattern of the sample. CONSTITUTION:A wafer 2 is moved with specified steps beforehand, and the place where the most favorable resolution is obtained is found and fixed. On a sensor, the opening 23 of a slit 5 can obtain a comb-shaped waveform 25 in response to the brightness of the light on each element in the sensor. The central addresses of the waveform 25 x1-x5 are obtained with a crossing point detection circuit. When the wafer b2 is moved, the waveform 25 is moved parallel to be a waveform 26, with the central address being x'1-x'5. The focus can be adjusted by moving the stage so that there is no displacement of the central address at the position where the central address is displaced in the reference position. With that method, plural slit images 23b are projected and focused on the surface of the wafer 2, and the average position of each slit image is a focused position. |
