23 March 2009 Process variation monitoring (PVM) by wafer inspection tool as a complementary method to CD-SEM for mapping LER and defect density on production wafers
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As design rules shrink, Critical Dimension Uniformity (CDU) and Line Edge Roughness (LER) constitute a higher percentage of the line-width and hence the need to control these parameters increases. Sources of CDU and LER variations include: scanner auto-focus accuracy and stability, lithography stack thickness and composition variations, exposure variations, etc. These process variations in advanced VLSI manufacturing processes, specifically in memory devices where CDU and LER affect cell-to-cell parametric variations, are well known to significantly impact device performance and die yield. Traditionally, measurements of LER are performed by CD-SEM or Optical Critical Dimension (OCD) metrology tools. Typically, these measurements require a relatively long time and cover only a small fraction of the wafer area. In this paper we present the results of a collaborative work of the Process Diagnostic & Control Business Unit of Applied Materials® and Nikon Corporation®, on the implementation of a complementary method to the CD-SEM and OCD tools, to monitor post litho develop CDU and LER on production wafers. The method, referred to as Process Variation Monitoring (PVM), is based on measuring variations in the light reflected from periodic structures, under optimized illumination and collection conditions, and is demonstrated using Applied Materials DUV brightfield (BF) wafer inspection tool. It will be shown that full polarization control in illumination and collection paths of the wafer inspection tool is critical to enable to set an optimized Process Variation Monitoring recipe.
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Saar Shabtay, Saar Shabtay, Yuval Blumberg, Yuval Blumberg, Shimon Levi, Shimon Levi, Gadi Greenberg, Gadi Greenberg, Daniel Harel, Daniel Harel, Amiad Conley, Amiad Conley, Doron Meshulach, Doron Meshulach, Kobi Kan, Kobi Kan, Ido Dolev, Ido Dolev, Surender Kumar, Surender Kumar, Kalia Mendel, Kalia Mendel, Kaori Goto, Kaori Goto, Naoaki Yamaguchi, Naoaki Yamaguchi, Yasuhiro Iriuchijima, Yasuhiro Iriuchijima, Shinichi Nakamura, Shinichi Nakamura, Shirou Nagaoka, Shirou Nagaoka, Toshiyuki Sekito, Toshiyuki Sekito, } "Process variation monitoring (PVM) by wafer inspection tool as a complementary method to CD-SEM for mapping LER and defect density on production wafers", Proc. SPIE 7272, Metrology, Inspection, and Process Control for Microlithography XXIII, 72720O (23 March 2009); doi: 10.1117/12.814063; https://doi.org/10.1117/12.814063

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