| 摘要 |
PURPOSE:To improve the utilization rate of a laser light source and to simplify the constitution of a device by irradiating a 1st positioning mark composed of a phase diffraction grating with a coherent light beam and converging two projected diffracted light beams on a 2nd positioning mark. CONSTITUTION:A positioning mark PT1 provided on a reticle 11 consists of a slit part S1, light shield parts S21 and S22 adjoining to it, and a light transmission part S23, where a lambda/2 plate X1 is embedded. Therefore, when laser light LA is projected, light beams passed through the slit part 21 and transmission part S23 interfere with each other to project (+ or -1)th-order diffracted light beams LA+1 and LA-1. Further, (0)-th-order light passed through the slit S1 is canceled by light transmitted through the transmission part S23. Thus, the (+ or -)th-order diffracted light beams form interference fringes on a positioning mark PT2 formed of a diffraction grating on a semiconductor wafer 13. The interference fringe image is diffracted by the pattern of the mark PT2 and made incident on a light intensity detector 14. Then the wafer 13 is so moved that the detected light LADET has specific intensity, thereby positioning the wafer at the reticle 11. |
