Methodology for improved semiconductor process monitoring using optical emission spectroscopy
First Claim
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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Abstract
In a semiconductor process which utilizes a plasma within a process tool chamber, a method of using optical emission spectroscopy (OES) to monitor a particular parameter of the process is disclosed. A first wavelength present in the plasma is determined which varies highly in intensity depending on the particular parameter by observing a statistically significant sample representing variations of the particular parameter. A second wavelength of chemical significance to the process is also determined which is relatively stable in intensity over time irrespective of variations of the particular parameter, also by observing a statistically significant sample representing variations of the particular parameter. These two wavelengths may be determined from test wafers and off-line physical measurements. Then, the intensity of the first and second wavelengths present in the plasma is measured on-line during normal processing within the process tool chamber, and the ratio between the first and second wavelength'"'"'s respective intensities generates a numeric value which is correlated to the particular parameter. As an example, such a method may be used to generate a reliable alarm signal indicating the presence of etch stop conditions within a plasma oxide etcher, as well as to indicate the oxide etch rate.
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Citations
12 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification