Step and repeat camera

Figure 2. Modulation Transfer Functions (MTF s) for the Perkin Elmer Micralign cameras operating at 250 nm, 300 nm and 400 nm, and for a step-and-repeat camera lens with a numerical aperture of 0.35.

Bouwer, G. Bouwhuis, H. Van Heek, and S. Wittkoek, The sihcon repeater, Philips Tech. Rev. 37(11/12), 330 333 S. Wittkoek, Optical aspects of the silicon repeater, Philips Tech. Rev. 41, 268 (1983/84) H. Binder and M. Lacomhat, Step and repeat projection printing for VLSI circuit fahrication, IEEE Trans. Electron Dev. ED-26(4), 698 704 (1979) J. Wilcyncski, Optical step and repeat camera with dark field automatic alignment, J. Vac. Sci. Technol. 16,1929 1933 (1979). 

Step-and-repeat (S/R) cameras use refractive lenses with numerical apertures of 0.2 to 0.4. The best lenses expose a field of about 2 cm x 2 cm at a numerical aperture of 0.3. Higher numerical aperture is available for smaller field-size. The field-size and numerical aperture for many of the lenses used in microcircuit cameras are shown in Figure 3. Most lenses are designed to operate at a single wavelength that corresponds to a strong line in the mercury spectrum (365 nm, 405 nm, or 436 nm), but lenses have also been corrected for two wavelengths (405 nm and 436 nm) in order to reduce the effects of... 

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