| 摘要 |
PURPOSE:To reduce the shift of a mark detecting position, and realize highly precise mark position detection, by photoelectrically detecting two higher order diffraction lights out of diffraction lights generated from a diffraction grating type mark, and adding the lights after amplification. CONSTITUTION:In order to defect an inclined grating type mark M which is used for alignment in the X-direction, photoelectric detectors PDL, PDR are arranged so as to interpose a center line CL of the mark M in the X-direction and be shifted in the Y-direction. When the center line in the width direction (X-direction) of a spot light coincides with the line CL, the detector PDR receives diffraction light (e.g. positive diffraction light) PK1 which is generated at an obliquely right upper part of the mark M. The detector PDL receives diffraction light (e.g. negative diffraction light) PK2 which is generated at an obliquely left lower part. After photoelectric signals A1 and A2 of the detectors PDR and PDL are amplified with amplifiers AP1 and AP2 capable of gain adjustment, the outputs are load with an adder, and processed as the diffraction signal from the mark M. Thereby precise alignment is realized even when the light reflection state of the mark is changed by the influence of a process. |
