Monitoring radical particle concentration using mass spectrometry

1. A system for monitoring radical particles comprising:

a test chamber configured to be coupled to a flow channel adapted to transmit a gas, the test chamber defining an aperture connecting the test chamber and the flow channel, the aperture configured to permit a subset of the gas to enter the test chamber from the flow channel;

an ionizer positioned within the test chamber, the ionizer configured to generate radical ions from radical particles of the subset of the gas; and

a mass spectrometer configured to measure a quantity of the radical ions.

2. The system of claim 1 , wherein the mass spectrometer is a residual gas analyzer (RGA).

3. The system of claim 1 , wherein the test chamber is configured to maintain a gas pressure lower than a gas pressure at the flow channel.

4. The system of claim 3 , wherein the gas pressure in the test chamber is less than 1e-2 Torr, and the gas pressure in the flow channel is greater than 0.01 Torr.

5. The system of claim 1 , wherein the ionizer is positioned within 4 inches of the aperture.

6. The system of claim 1 , wherein the ionizer is configured to operate at a low-energy state to generate the radical ions and minimize generation of non-radical ions, the low-energy state being lower than an energy state associated with the generation of the non-radical ions.

7. The system of claim 1 , wherein the ionizer is configured to operate at a plurality of low-energy states, each of the plurality of low-energy states corresponding to a respective radical particle.

8. The system of claim 1 , wherein the ionizer is configured to operate at a high-energy state to enable acquisition of a reference signal based on non-radical particles of the subset of the gas.

9. The system of claim 1 , wherein the aperture has a diameter of less than 1 millimeter.

10. The system of claim 1 , wherein the aperture permits passage, to the test chamber, a ratio of radical particles to non-radical particles that is greater than 0.1% of the ratio present in the gas within the flow channel.

11. The system of claim 1 , further comprising a protrusion of the test chamber extending into the flow channel and encompassing a volume of the test chamber, the aperture being positioned at the protrusion.

12. The system of claim 11 , wherein the protrusion exhibits a substantially conical shape, the aperture being positioned at a point of the conical shape.

13. The system of claim 12 , wherein the ionizer is positioned to generate radical ions within a volume defined by the conical shape.

14. The system of claim 13 , wherein the conical shape is configured as an electrostatic element of the ionizer.

15. The system of claim 13 , further comprising an electrostatic lens configured to direct the radical ions as a beam towards the mass spectrometer.

16. The system of claim 1 , further comprising a controller configured to control operation of a radical particle source based on the quantity of the radical ions measured by the mass spectrometer.

17. The system of claim 16 , wherein controlling the operation of the radical particle source includes controlling at least one of 1) quantity of radical particle generation over a given time and 2) a time period in which the radical particles are generated.

18. The system of claim 16 , wherein controlling the operation of the radical particle source includes controlling at least one of power, gas flow, gas pressure, and temperature of a wetted path of the flow channel.

19. The system of claim 1 , further comprising a stopper configured to selectively seal the aperture.

20. The system of claim 1 , wherein a surface encompassing the aperture is non-metal and exhibits a reactivity and recombination coefficient for the radical particles that is lower than that of a metal surface.

21. The system of claim 1 , wherein a surface encompassing the aperture is metallic and exhibits low reactivity with the radical particles.

22. The system of claim 1 , wherein the flow channel is a conduit extending from a radical source to a process chamber.

23. The system of claim 1 , wherein the flow channel is a region down-stream of a reaction zone in a process chamber.

24. The system of claim 1 , wherein the flow channel is a conduit down-stream of a process chamber.

25. A method of monitoring radical particles comprising:

directing a subset of a gas from a flow channel to a test chamber via an aperture connecting the test chamber and the flow channel;

generating, via an ionizer, radical ions from radical particles of the subset of the gas; and

measuring, via a mass spectrometer, a quantity of the radical ions.

26. The method of claim 25 , wherein the mass spectrometer is a residual gas analyzer (RGA).

27. The method of claim 25 , further comprising maintaining a gas pressure at the test chamber that is lower than a gas pressure at the flow channel.

28. The method of claim 27 , wherein the gas pressure in the test chamber is less than 1e-2 Torr, and the gas pressure in the flow channel is greater than 0.01 Torr.

29. The method of claim 25 , wherein the ionizer is positioned within 4 inches of the aperture.

30. The method of claim 25 , further comprising operating the ionizer at a low-energy state to generate the radical ions and minimize generation of non-radical ions, the low-energy state being lower than an energy state associated with the generation of the non-radical ions.

31. The method of claim 25 , further comprising operating the ionizer at a plurality of low-energy states, each of the plurality of low-energy states corresponding to a respective radical particle.

32. The method of claim 25 , further comprising operating the ionizer at a high-energy state to enable acquisition of a reference signal based on non-radical particles of the subset of the gas.

33. The method of claim 25 , wherein the aperture has a diameter of less than 1 millimeter.

34. The method of claim 25 , wherein the aperture permits passage, to the test chamber, a ratio of radical particles to non-radical particles that is greater than 0.1% of the ratio present in the gas within the flow channel.

35. The method of claim 25 , wherein a protrusion of the test chamber extends into the flow channel and encompassing a volume of the test chamber, the aperture being positioned at the protrusion.

36. The method of claim 35 , wherein the protrusion exhibits a substantially conical shape, the aperture being positioned at a point of the conical shape.

37. The method of claim 36 , further comprising operating the ionizer to generate radical ions within a volume defined by the conical shape.

38. The system of claim 37 , wherein the conical shape is configured as an electrostatic element of the ionizer.

39. The method of claim 37 , further comprising directing, via an electrostatic lens, the radical ions as a beam towards the mass spectrometer.

40. The method of claim 25 , further comprising controlling operation of a radical particle source based on the quantity of the radical ions measured by the mass spectrometer.

41. The method of claim 40 , wherein controlling the operation of the radical particle source includes controlling at least one of 1) quantity of radical particle generation over a given time and 2) a time period in which the radical particles are generated.

42. The method of claim 40 , wherein controlling the operation of the radical particle source includes controlling at least one of power, gas flow, gas pressure, and temperature of a wetted path of the flow channel.

43. The method of claim 25 , further comprising selectively sealing the aperture via a stopper.

44. The method of claim 25 , wherein a surface encompassing the aperture is non-metal and exhibits a reactivity and recombination coefficient for the radical particles that is lower than that of a metal surface.

45. The method of claim 25 , wherein a surface encompassing the aperture is metallic and exhibits low reactivity with the radical particles.

46. The method of claim 25 , wherein the flow channel is a conduit extending from a radical source to a process chamber.

47. The method of claim 25 , wherein the flow channel is a region down-stream of a reaction zone in a process chamber.

48. The method of claim 25 , wherein the flow channel is a conduit down-stream of a process chamber.