Holographic mask aligners represent the latest addition to commercially available lithographic technologies. Their combination of very high resolution (< 0.5 μm) and very large exposure field brings a new capability to the microelectronics industry, especially for the manufacture of flat panel displays. The machine is fully automated and includes a scanning laser illumination system, a dynamic focus system permitting patterns to be printed over poor-flatness substrates, and an alignment system providing 0.3-μm overlay accuracy. A higher-accuracy alignment system under development demonstrates 50-nm measurement accuracy. A step-and-repeat hologram recording method enables tighter control of feature linewidth.
Francis S. M. Clube,
"Holographic microlithography," Optical Engineering 34(9), (1 September 1995). http://dx.doi.org/10.1117/12.205673