| 摘要 |
PURPOSE:To observe a wafer directly and to make it possible to perform detection without considering the deterioration in transmittance, by inserting observing optical systems between the wafer and an exposing optical system, and keeping a magnification and focus unchanged. CONSTITUTION:Observing optical systems 41, 5 and 42 are inserted between wafer 2 and an exposing optical system 40. The magnification and the focus of a projected image are kept unchanged eve if the systems are inserted. The wafer can be directly observed without using the exposing optical system 40. This is an advantage. When the numerical aperture NA of the exposing optical system s small, high alignment accuracy is required. In this case, how the wafer can be observed with good resolution becomes a problem. The system, which directly observes the wafer, can detect light with a numerical aperture NA larger than the numerical aperture NA of the exposing optical system. Therefore, said system is more advantageous in comparison with a method using the exposing optical system. Since the wafer can be directly detected without considering the deterioration due to the transmittance of the exposing optical system 40, this method is advantageous when the transmittance is poor. |
