Method of reducing process plasma damage using optical spectroscopy
AssigneeLSI Logic Corporation
InventorsShiqun Gu, Peter Gerard McGrath, Ryan Tadashi Fujimoto
Life of this patent
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Abstract
Optical emission spectra from a test wafer during a plasma process are measured using a spectrometer. The plasma charging voltage retained by (detected by) the test wafer is measured after the process step is completed. The emission spectra are correlated with the plasma charging voltage to identify the species contributing to the plasma charging voltage. The optical emission spectra are monitored in real time to optimize the plasma process to prevent plasma charging damage. The optical emission spectra are also monitored to control the plasma process drift.
Claims17
A method for determining process species associated with plasma charging damage, the method comprising:
- measuring a first optical emission spectrum from a plasma directed to a test wafer during a plasma process operation;
- measuring a plasma induced charge level on the test wafer;
- correlating the optical emission spectrum with the plasma induced charge level;
- and
- from the correlation, identifying a molecular species contributing to the plasma induced charge level.
A method for adjusting plasma charge levels on a wafer during a plasma process step by monitoring the optical emission spectral output, the method comprising:
- a) measuring a first optical emission spectrum correlated with plasma charging on a wafer during the a plasma process step;
- b) using correlation data to determine a plasma induced charge level on the wafer from the measured optical spectrum;
- and
- c) adjusting a plasma process parameter in response to the measured first optical emission spectrum when the plasma induced charge level exceeds a predetermined threshold.
A method for monitoring plasma process variation, the method comprising:
- performing a first and second measurement of an optical emission spectrum correlated with plasma charging from at least one wafer during a plasma process step;
- and
- determining the relative plasma charge levels on the at least one wafer at the time of the measurements from the the first and second measurements.
Dependencies are inferred from the claim text.