POSITIONING APPARATUS WITH DIFFRACTION GRATING

摘要

PURPOSE:To easily and accurately set a relative position or gap between two objects for highly accurate positioning by providing a deflection mirror which changes an incident angle of beam entering the first lens and also providing a first diffraction grating to the image space focal point of the second lens. CONSTITUTION:The laser beam reaches an optical system consisting of a first lens 31 and a second lens 32 having the equal focal distance arranged at the confocal position. An incident angle deflection mirror 16 is arranged at the focal distance of a first lens 31 and a first diffraction grating 5 is arranged at the focal distance of a second lens 32. The beam is deflected for desired angle by the mirror 16 and becomes the parallel beam between the first lens 31 and the second lens 32 and then enters the diffraction grating 5. The light diffracted by the diffraction gratings 5, 8 converted to the parallel beam by the second lens 32. It is reflected by a half mirror 18 and enters the photoelectric surface of the photoelectric converters 12, 13 through a condenser lens 11. The converted detection signal is sent as a control signal after calculation at the controller 14 for high precision positioning between the mask 4 and wafer 7.