Methods of measuring overlay errors in area-imaging e-beam lithography

摘要

One embodiment relates to a method of measuring overlay errors for a programmable pattern, area-imaging electron beam lithography apparatus. Patterned cells of an overlay measurement target array may be printed in swaths such that they are superposed on patterned cells of a first (base) array. In addition, the overlay array may have controlled-exposure areas distributed within the swaths. The superposed cells of the overlay and base arrays are imaged. The overlay errors are then measured based on distortions between the two arrays in the image data. Alternatively, non-imaging methods, such as using scatterometry, may be used. Another embodiment relates to a method for correcting overlay errors for an electron beam lithography apparatus. Overlay errors for a pattern to be printed are determined based on within-swath exposure conditions. The pattern is then pre-distorted to compensate for the overlay errors. Other embodiments, aspects and features are also disclosed.