| 摘要 |
PURPOSE:To obtain an accurate, high-efficiency positioning device by projecting a variable-length elliptic spot on an object which has a pattern. CONSTITUTION:Luminous flux emitted by a light source 4 is collimated by a collimator lens 5 into parallel luminous flux to form an elliptic spot on the object 10 through a cylindrical lens 8, and then scattered light is detected by a couple of detectors 11. Here, the diaphragm which consists of a fixed aperture 6 and apertures 7 and 7' capable of shifting in position in a generator direction is interposed in the luminous flux from the lens 5 to vary the lengthwise length of the elliptic spot formed on the object 10. Consequently, even if the wafer has a rotation-directional position error, the spot is not projected on the pattern of a chip when the spot reaches a street line by making the lengthwise length of the spot 3 nearly equal to one side of the chip; and a clear maximal value appears in the photoelectric signal of the scattered line and the street line is clearly detected. |
