| 摘要 |
PURPOSE:To execute an alignment with high accuracy by arranging a monochromatic light beam to be incident in a direction oblique to a normal in the plane containing a first and a second diffraction gratings and the normal to the grating surface, and detecting a diffracted light beam in an oblique direction. CONSTITUTION:A monochromatic light beam 33 is reflected by a mirror 27 and made incident on a mark (diffraction grating) 30 of a mask 26. Its direction is vertical to a segment AA' in a surface B'OC' and makes an angle theta with a segment CC'. That is, it is vertical to the pitch direction of the grating 30 and makes an angle thetaat a grating line B' side against a normal of a grating surface. Accordingly, + or -primary diffracted light beams 34, 25 are diffracted in the symmetrical primary diffraction angle direction centering around the normal CC'. In this state, from the sum or a difference of optical intensity signals of the primary diffracted light beams 34, 35 obtained by photoelectric converters 28, 29 against a displacement in the pitch direction of the diffraction grating, a wafer 26' (grating 30') and the mask 26 (grating 30') can be aligned. The mirror 27 and the photoelectric converters 28, 29 are placed in the outside of an exposure area 32, the mask mark 30 can be placed adjacently in an LSI pattern area 31, the alignment can be executed with high accuracy, and a mechanism of a detecting optical system and a mechanism control system can be simplified. |
