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Methodology for improved semiconductor process monitoring using optical emission spectroscopy

  • US 6,046,796 A
  • Filed: 04/22/1998
  • Issued: 04/04/2000
  • Est. Priority Date: 04/22/1998
  • Status: Expired due to Fees
First Claim
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1. In a semiconductor process which utilizes a plasma within a process tool chamber, a method of using optical emission spectroscopy (OES) to determine whether etch stop conditions are present within the chamber, the method comprising:

  • first determining a first wavelength present in the plasma which varies highly in intensity depending on whether etch stop conditions are present within the chamber, and also determining a second wavelength of chemical significance to the etching process which is relatively stable in intensity over time irrespective of whether etch stop conditions are present within the chamber, determining both wavelengths by observing a statistically significant sample representing variations of the etching process, wherein the first and the second wavelength are determined by;

    first running a statistically significant sample of wafers representing variations of the etching process without etch stop conditions present within the chamber, and measuring OES data for each wafer;

    periodically performing physical measurements of etching parameters;

    thenrunning a second sample of wafers while intentionally inducing etch stop conditions within the chamber, and measuring OES data for each wafer of this second sample; and

    statistically correlating the OES data against the physical measurement to determine both the first wavelength present in the plasma which varies highly in intensity depending on whether etch stop conditions are present within the chamber, and to determine the second wavelength of chemical significance to the process which is relatively stable in intensity over time irrespective of whether etch stop conditions are present within the chamber;

    thenmeasuring the intensity of the first and second wavelengths present in the plasma on-line during normal processing within the process tool chamber; and

    ratioing the first and second wavelength'"'"'s respective intensities to generate a numeric value which is correlated to the presence of etch stop conditions within the chamber.

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