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Monitoring and controlling plasma processes via optical emission using principal component analysis

  • US 5,658,423 A
  • Filed: 11/27/1995
  • Issued: 08/19/1997
  • Est. Priority Date: 11/27/1995
  • Status: Expired due to Fees
First Claim
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1. A method for monitoring the status of a plasma using real-time spectral data obtained while conducting an etch process in the course of manufacturing a semiconductor wafer, said method comprising the steps of:

  • a) collecting said spectral data during said etch process from said plasma;

    b) calculating principal components of said collected spectral data and determining a control limit characteristic of said etch process;

    c) extracting from said plasma additional spectral data;

    d) forwardly, and subsequently backwardly projecting said forwardly projected additional spectral data utilizing said principal components;

    e) subtracting said additional spectral data from said backwardly projected data, resulting in a data set of residuals; and

    f) combining said residuals and comparing said combined residuals to said control limits, whereina fault in said etch process is detected when the result of said comparison exceeds said control limit.

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