Air leak detection in plasma processing apparatus with separation grid
Plasma processing apparatus and associated methods for detecting air leak are provided. In one example implementation, the plasma processing apparatus can include a processing chamber to process a workpiece, a plasma chamber separated from the processing chamber by a separation grid, and an inductive coupling element to induce an oxygen plasma using a process gas in the plasma chamber. The plasma processing apparatus can detect afterglow emission strength from reaction between nitric oxide (NO) and oxygen radical(s) in a process space downstream to an oxygen plasma to measure nitrogen concentrations due to presence of air leak.
1. A method of detecting presence of nitrogen in a plasma processing apparatus, the method comprising:
admitting an oxygen-containing gas into a plasma chamber;
generating one or more species from the oxygen-containing gas in the plasma chamber, the one or more species comprising an oxygen plasma;
filtering the one or more species to create a mixture via a separation grid that separates the plasma chamber from a processing chamber located downstream of the plasma chamber, the mixture comprising one or more oxygen radicals, wherein the oxygen plasma is contained in the plasma chamber such that the mixture in the processing chamber is separated from the oxygen plasma via the separation grid;
obtaining data associated with luminescence generated in the processing chamber, wherein the luminescence is emitted from excited nitrogen dioxide molecules located downstream from the oxygen plasma; and
determining the presence of nitrogen in the plasma processing apparatus based at least in part on the data associated with the luminescence corresponding to a peak wavelength of 600-615 nanometers.
2. The method of claim 1 , wherein the excited nitrogen dioxide molecules are generated by reaction of nitric oxide recombining with the one or more oxygen radicals in the processing chamber.
3. The method of claim 2 , wherein the nitric oxide is generated by one or more nitrogen molecules reacting with the one or more oxygen radicals.
4. The method of claim 1 , wherein determining the presence of nitrogen comprises determining a concentration of nitrogen in the plasma processing apparatus.
5. The method of claim 1 , wherein the nitrogen is in the plasma chamber.
6. The method of claim 1 , wherein the nitrogen is in the processing chamber.
7. The method of claim 1 , wherein the data associated with the luminescence is obtained from a location between the separation grid and a workpiece support in the processing chamber.
8. The method of claim 1 , wherein the data associated with the luminescence is obtained from a location proximate to a gas exhaust port for evacuating a gas from the processing chamber.
9. The method of claim 1 , wherein the data associated with the luminescence is obtained from an optical emission spectroscopy (OES) probe that is connected to an optical view port on the processing chamber.
10. The method of claim 1 , wherein the data associated with the luminescence comprises an optical emission spectrum comprising wavelengths in a range of about 400 nanometers to about 1400 nanometers.
11. The method of claim 1 , wherein the data associated with the luminescence comprises optical emission data obtained from a multi-wavelength end point detector.
12. The method of claim 1 , wherein the data associated with the luminescence comprises optical emission data obtained from a single-wavelength end point detector.
13. The method of claim 1 , further comprising exposing the mixture to a workpiece.
14. The method of claim 4 , wherein determining the concentration of nitrogen in the plasma processing apparatus comprises:
for each time point of a plurality of time points during a time period,
determining a background by averaging intensities of a first portion of the data associated with the luminescence, wherein the data associated with the luminescence comprises an optical emission spectrum;
subtracting the background from a second portion of the optical emission spectrum, wherein the second portion comprises higher wavelengths than the first portion;
integrating subtracted second portion of the optical emission spectrum to obtain an integrated intensity at that time point;
averaging a plurality of integrated intensities obtained during the time period to obtain a time-averaged integrated intensity, each of the plurality of integrated intensities associated with each time point; and
comparing the time-averaged integrated intensity with a model correlating nitrogen concentration with time-averaged integrated intensity to determine the nitrogen concentration.
15. The method of claim 14 , wherein the first portion of the optical emission spectrum comprises wavelengths is in a range of about 200 nanometers to about 350 nanometers.
16. The method of claim 14 , wherein the second portion of the optical emission spectrum comprises wavelengths in a range of about 400 nanometers to about 750 nanometers.
17. The method of claim 14 , wherein the model is obtained from a plurality of optical emission spectra, each of the plurality of optical emission spectra associated with a known nitrogen concentration.