Articles you may be interested inFast aerial image simulations using one basis mask pattern for optical proximity correctionWe describe a unified approach to measuring alignment and gap with nanometer detectivity between two planar objects ͑e.g., a mask and a substrate͒ in close proximity. The method encodes lateral position in the phase of interference fringes, formed by diffraction from grating and checkerboard alignment marks, designed to enable a wide acquisition range. For gapping, the method incorporates, in the same mark, coarse-gap detection ͑30-300 m͒ and absolute-gap detection at sub-30 m using a chromatic Fabry-Pérot scheme. Fine detection of sub-30 m gaps is inferred from the frequency and phase of fringes, calibrated using the chromatic Fabry-Pérot. Illumination with a variable-bandwidth source enables either ''achromatic'' aligning or ''chromatic'' gapping. Sub-nanometer detection and feedback control of mask position is demonstrated in X, Y, and . Overlay of exposed patterns is demonstrated to be Ͻ3 nm.
Electron beam and optical proximity effect reduction for nanolithography: New results J.We describe a noncontact, optical method of measuring, with nanometer-level sensitivity, the gap between two planar objects in close proximity, such as a substrate and either a proximity-lithography mask or an imprint template. Interference fringes from a chirped-checkerboard mark on one object are observed using a nonexposing wavelength with long-working-distance, oblique-incidence microscopes. The gap is determined from the spatial frequency and phase of the fringes. We verify the gap measurement using a variation of the Talbot effect with the chirped-checkerboard mark. The two forms of gap measurement are complementary since one is suited to measuring and setting gap prior to exposure, and the other is ideal for confirmation of the gap that existed during exposure.
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