Positioning technology in X-ray lithography

X-ray lithography is expected to become one of the most powerful technologies in future ultralarge-scale integrated circuit fabrication. Because very short wavelengths of about 1 nm are used in printing, X-ray lithography has excellent potential to produce resolution of less than one hundred nanometers. This can be achieved by using an appropriate wavelength with proper mask contrast for X-rays and by providing a small mask-to-wafer gap. However, extremely accurate overlay between circuit pattern layers, as well as a small mask-to-wafer gap, is necessary to take full advantage of the excellent resolution able to be obtained in printing small structures. So accurate position detection and mechanical positioning are critical in advanced X-ray lithography systems, almost all of which require nanometer-order precision. This paper describes accurate alignment and positioning technologies for an X-ray lithography system.