8 June 1998 Matching analysis on seven manufacturing CD SEMs
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Abstract
The control of critical dimensions is of primary importance in a semiconductor manufacturing line. While the use of level- dedicated CDSEMs assures maximum process control, it is preferable to use multiple CDSEMs interchangeably to minimize the effect of any CDSEM unavailability caused by systems being down, preventive maintenance, or when maximum flexibility and enhanced production throughput are required. Maintaining process control while measuring on multiple CDSEMs requires that CDSEM tool-to-tool matching of less than 5 nm be achieved and maintained. This paper describes a methodology whereby a seven-system CDSEM toolset is initially baselined to determine the subset(s) of systems which most closely match. A method of evaluating the inherent matching of seven OPALTM7830i CDSEMs within a single manufacturing facility is presented. The matching analysis was performed using a single production- level wafer, a level known to have previously exhibited poor matching results. All seven CDSEMs were networked to a common database server to insure that all measured consistently across the toolset. An experiment is described to ascertain the effects of multiple electron-beam measurements on this semiconductor sample and to evaluate any relative dimensional changes. A methodology for monitoring and controlling CDSEM system parameters during the matching evaluation is described. Finally, a procedure for determining the subset(s) of matched CDSEMs using analysis-of-variance (ANOVA), least significant difference (LSD, also known as a pairwise t-test) and Duncan's Multiple Range Test is presented. Using these methods, three subsets of systems are defined within the seven-system toolset that exhibited similar matching performance.
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Reginald R. Bowley, James E. Beecher, Robert M. Cogley, Sandra R. Dupuis, Dewey L. Farrington, "Matching analysis on seven manufacturing CD SEMs", Proc. SPIE 3332, Metrology, Inspection, and Process Control for Microlithography XII, (8 June 1998); doi: 10.1117/12.308719; https://doi.org/10.1117/12.308719
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