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Exposure focus leveling method using region-differentiated focus scan patterns

  • US 10,209,636 B1
  • Filed: 03/07/2018
  • Issued: 02/19/2019
  • Est. Priority Date: 03/07/2018
  • Status: Active Grant
First Claim
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1. A method of operating a lithographic exposure tool, comprising:

  • forming semiconductor dies arranged in a plurality of rows and columns in an array on a substrate, wherein the array has a first periodicity along a first horizontal direction and a second periodicity along a second horizontal direction within a horizontal plane that is parallel to a top surface of the substrate, and each semiconductor die includes a first image region and a second image region having a different pattern of structural components than the first image region;

    applying a photoresist layer over the semiconductor dies;

    loading the substrate on a stage in the lithographic exposure tool;

    generating a first map of first optimal focus distances along first scan paths that extend along the first horizontal direction and over the first image regions of the semiconductor dies on the substrate, wherein the first scan paths do not cross any of the second image regions of the semiconductor dies;

    generating a second map of second optimal focus distances along second scan paths that extend along the first horizontal direction and over the second image regions of the semiconductor dies on the substrate, wherein the second scan paths do not cross any of the first image regions of the semiconductor dies; and

    leveling the substrate with respect to an optics system of the lithographic exposure tool.

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