System, method and apparatus for using optical data to monitor RF generator operations

• US 9,627,186 B2
• Filed: 11/25/2014
• Issued: 04/18/2017
• Est. Priority Date: 08/29/2014
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Valcore, Jr., John C., San, Tony, Lee, Seonkyung
• Primary Examiner(s): LEE, JOHN R
• Application Number:
  US14/554,006
• Publication Number:
  US 20160064199A1
• Time in Patent Office: 875 Days
• CPC Class Codes: G01J 1/42 using electric radiation detectors optical or mechanical part G01J1/04; by comparison with a reference light or electric value G01J1/10
• CPC Class Codes: H01J 37/32183 Matching circuits
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32972 Spectral analysis

Abstract

A system and method monitoring a plasma with an optical sensor to determine the operations of a pulsed RF signal for plasma processing including a plasma chamber with an optical sensor directed toward a plasma region. An RF generator coupled to the plasma chamber through a match circuit. An RF timing system coupled to the RF generator. A system controller is coupled to the plasma chamber, the RF generator, the optical sensor, the RF timing system and the match circuit. The system controller includes a central processing unit, a memory system, a set of RF generator settings and an optical pulsed plasma analyzer coupled to the optical sensor and being capable to determine a timing of a change in state of an optical emission received in the optical sensor and/or a set of amplitude statistics corresponding to an amplitude of the optical emission received in the optical sensor.

Claims

1. A plasma processing system comprising:

a plasma chamber having a plasma region associated with an optical sensor that is directed toward the plasma region, wherein the optical sensor is configured to capture an optical emission from the plasma region, and the optical sensor produces an output sensor signal for the optical emission;

at least one RF generator coupled to the plasma chamber through a match circuit;

an RF timing system coupled to the at least one RF generator, wherein the RF timing system is configured to generate a timing reference signal; and

a system controller coupled to the optical sensor, wherein the system controller is configured to process an optical pulsed plasma analyzer, wherein the optical pulsed plasma analyzer is configured to receive the output sensor signal from the optical sensor and is further configured to determine a set of amplitude statistics corresponding to an amplitude of the optical emission captured by the optical sensor, wherein to determine the set of amplitude statistics, the optical pulsed plasma analyzer is configured to,

subdivide a state of the timing reference signal into a plurality of time intervals; and

identify an amplitude statistic of the output sensor signal for each of the time intervals to control a setting of the at least one RF generator.

2. The system of claim 1, wherein the optical pulsed plasma analyzer is configured to determine a time of a change in a state of the output sensor signal by determining that an amplitude of the output sensor signal within a sample duration window exceeds a selected set point at the time.

3. The system of claim 2, wherein the sample duration window is offset a selected amplitude from a pretrigger average amplitude, wherein the output sensor signal is settled at the pretrigger average amplitude before a time of transition of the timing reference signal from an additional state to the state.

4. The system of claim 2, wherein the sample duration window is delayed by a selected time delay.

5. The system of claim 2, wherein the optical pulsed plasma analyzer is configured to select the sample duration window for determining the time of the change in the state of the output sensor signal.

6. The system of claim 1, wherein the optical pulsed plasma analyzer is configured to determine a change in amplitude of the output sensor signal a plurality of times within a selected sample duration window.

7. The system of claim 1, wherein the system controller includes a memory system coupled to the optical pulsed plasma analyzer for storing the amplitude statistic of the output optical sensor signal for each of the time intervals.

8. A plasma processing system comprising:

a plasma chamber having a plasma region associated with an optical sensor, wherein the optical sensor is directed toward the plasma region to capture an optical emission, wherein the optical sensor is configured to produce an output sensor signal upon capturing the optical emission;

an RF timing system configured to generate a timing reference signal; and

a system controller coupled to the plasma chamber, the optical sensor, and the RF timing system, wherein the system controller is configured to process an optical pulsed plasma analyzer, wherein the optical pulsed plasma analyzer is configured to determine a change in a state of the output sensor signal and a set of amplitude statistics corresponding to an amplitude of the optical emission captured by the optical sensor, wherein to determine the set of amplitude statistics, the optical pulsed plasma analyzer is configured to,

subdivide a state of the timing reference signal into a plurality of time intervals; and

determine an amplitude statistic of the output sensor signal for each of the time intervals.

9. A method comprising:

receiving an output sensor from an optical sensor, wherein the output sensor signal is generated when the optical sensor captures an optical plasma emission;

filtering the output sensor signal to produce a filtered optical signal;

rectifying the filtered optical sensor signal to produce a rectified and filtered output sensor signal;

determining a dynamic threshold level of the rectified and filtered output sensor signal occurring before a change in a state of a timing reference signal; and

detecting a change in a state of the rectified and filtered output sensor signal occurring after the change in the state of the timing reference signal; and

determining a set of amplitude statistics corresponding to an amplitude of the optical plasma emission captured by the optical sensor, wherein said determining the set of amplitude statistics includes;

subdividing the state of the timing reference signal into a plurality of time intervals; and

determining an amplitude statistic of the output sensor signal for each of the time intervals to control a setting of a radio frequency (RF) generator.

10. The method of claim 9, wherein detecting the change in the state of the rectified and filtered output sensor signal includes determining that an amplitude of the rectified and filtered output sensor signal within a sample duration window exceeds a selected set point.

11. The method of claim 10, wherein the sample duration window is offset a selected amplitude from a pretrigger average amplitude, wherein the rectified and filtered output sensor signal is settled at the pretrigger average amplitude before a time of transition of the timing reference signal from an additional state to the state.

12. The method of claim 10, wherein the sample duration window is delayed by a selected time delay.

13. The method of claim 10, further comprising selecting the sample duration window for determining a time of the change in the state of the rectified and filtered output sensor signal.

14. The method of claim 10, wherein said determining the change in the state includes determining a change in amplitude of the rectified and filtered output sensor signal a plurality of times within the sample duration window.

15. The method of claim 10, further comprising storing the amplitude statistic of the rectified and filtered output sensor signal for each of the time intervals.