Patent ID: 6344698
Filing Date: 2002-02-05
Classification: H01L

Abstract:
A robust alignment mark for use with exposure/alignment tools for improving the alignment accuracy, said alignment mark comprising: a set of geometrical shapes present on peripheral regions of a mask and wafer which are staggered in respect to each other so as to achieve additional left and right line edges in a small space and being arranged in a checkerboard configuration, wherein said geometrical shapes have outermost edges that are not visible to a detector and a size that is within the resolving capability of the exposure tool so that the geometrical shapes can be printed, yet the size of said shapes is smaller than the alignment tool's detector resolving capability resulting in the detector seeing only one overall image from the edges, said set of geometric shapes enhancing symmetrically aligned signals emitting from an asymmetric microstructure and being resistant to damages caused by subsequent semiconductor processing steps.