As scanner projection lens captures only a finite number of IC pattern diffraction orders. This low pass filtering leads to a range of optical proximity effects such as pitch-dependent CD variations, corner rounding and line-end pullback, resulting in imaged IC pattern excursions from the intended designs. These predictable OPEs are driven by the imaging conditions, such as wavelength, illuminator layout, reticle technology, and lens numerical aperture. To mitigate the pattern excursion due to OPEs, the photolithography community developed optical proximity correction methodologies, adopted and refined by the EDA industry. In the current implementations, OPC applied to IC designs can correct layouts to compensate for OPEs and to provide imaged patterns meeting the design requirements.
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