An alignment system for synchrotron radiation x-ray lithography

We have developed an alignment exposure system for synchrotron radiation (SR) x-ray lithography. The present system consists of vertical mask and wafer stages, optics for mask-to-wafer displacement detection, a feedback control system, and an aluminum chamber containing them. The chamber is filled with He gas in atmospheric pressure and separated by a 25-μm-thick Be window from the SR beam line in ultrahigh vacuum. The alignment method is based on an optical-heterodyne displacement detection using three diffraction gratings. With 1.0-μm-period gratings and a He–Ne transverse-mode Zeeman laser (wavelength=0.6328 μm), alignment precision better than 0.01 μm was achieved. Features and performance of the system are described.