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Interferometric lithography pattern delimited by a mask image

A Fourier optical system is used to address the problem of aperiodic pattern fabrication associated with interferometric lithography. The low frequency pattern defined by a pair of masks is modulated by the high- frequency interferometric pattern by splitting the optical path and introducing interferometric optics. This combined optical and interferometric system results in an image whose frequency content covers continuous high frequency regions instead of the discrete high frequency components associated with interferometric lithography. At the same time, resolution is characteristic of the interferometric rather than the optical exposure. This approach is in keeping with traditional optical lithography providing significantly enhanced pattern flexibility while still retaining the small-CD advantages of interferometric lithography. Experimental results are in good agreement with the model predictions of the product of the mask image and the interferometric line:space pattern.