Plasma etching process control
First Claim
1. Method of monitoring removal of a film on a product wafer during plasma etching, comprising:
- removing a film on a wafer, overlying an underlying material, by a plasma etching process with a plasma having an emission intensity, said film having an initial thickness prior to etching and a remaining thickness during etching;
while etching the film, monitoring the plasma emission intensity at a selected wavelength, said monitoring occurring non-perpendicularly to the wafer; and
correlating variations in the plasma emission intensity, attributable to reflected light interference phenomena, by observing a cyclic pattern in emission intensity, to the remaining film thickness.
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Abstract
A passive, in-line method of monitoring film removal (or deposition) during plasma etching (or deposition) based on interference phenomena is disclosed. Plasma emission intensity is monitored at a selected wavelength, without additional illuminating apparatus, and variations in plasma emission intensity are correlated to remaining film thickness, etch rate and uniformity, and etch selectivity. The method is useful in conjunction with nitride island etch, polysilicon etch, oxide spacer etch, contact etch, etc. The method is also useful in determining a particular remaining film thickness (e.g., just prior to clearing) at which point the etch recipe can be changed from a high-rate, low selectivity etch to a low-rate, high-selectivity etch.
93 Citations
12 Claims
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1. Method of monitoring removal of a film on a product wafer during plasma etching, comprising:
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removing a film on a wafer, overlying an underlying material, by a plasma etching process with a plasma having an emission intensity, said film having an initial thickness prior to etching and a remaining thickness during etching; while etching the film, monitoring the plasma emission intensity at a selected wavelength, said monitoring occurring non-perpendicularly to the wafer; and correlating variations in the plasma emission intensity, attributable to reflected light interference phenomena, by observing a cyclic pattern in emission intensity, to the remaining film thickness. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification