System, Method and Apparatus for Using Optical Data to Monitor RF Generator Operations

• US 20160064199A1
• Filed: 11/25/2014
• Published: 03/03/2016
• Est. Priority Date: 08/29/2014
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Valcore, John C. Jr., San, Tony, Lee, Seonkyung
• Granted Patent: US 9,627,186 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 at least one optical sensor directed toward a plasma region in the plasma chamber;

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; and

a system controller coupled to the plasma chamber, the at least one RF generator, the optical sensor, the RF timing system, and the match circuit, the system controller including;

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 at least one of 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.

2. The system of claim 1, wherein the set of amplitude statistics includes determining a change in amplitude of the optical emission within a selected sample duration window exceeds a selected set point.

3. The system of claim 2, wherein the selected sample duration window is offset a selected amplitude from a pretrigger average amplitude.

4. The system of claim 1, wherein the selected sample duration window is delayed for a selected group delay.

5. The system of claim 1, wherein determining the timing of the change in state of the optical emission received in the optical sensor includes selecting a sample window duration for determining the timing of the change in state of the optical emission.

6. The system of claim 1, wherein the set of amplitude statistics includes determining a change in amplitude of the optical emission a plurality of times within a selected sample duration window.

7. The system of claim 1, wherein the set of amplitude statistics includes:

subdividing at least one phase of a timing reference signal into a plurality of subdivisions;

determining an amplitude statistic of the output optical sensor signal for each of the subdivisions; and

storing the amplitude statistic of the output optical sensor signal for each of the subdivisions.

8. A plasma processing system comprising:

a plasma chamber having at least one optical sensor directed toward a plasma region in the plasma chamber;

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; and

a system controller coupled to the plasma chamber, the at least one RF generator, the optical sensor, the RF timing system, and the match circuit, the system controller including;

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 change in state of an optical emission received in the optical sensor.

9. A method of determining a change in state of an optical emission received in an optical sensor comprising:

receiving an optical plasma emission in an optical sensor;

outputting an optical sensor signal;

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

rectifying the filtered optical sensor signal to produce a rectified, filtered optical sensor signal;

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

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

storing the detected change in state of the rectified, filtered optical sensor signal.

10. The method of claim 9, wherein detecting the change in state of the rectified, filtered optical sensor signal occurring after the change in state of the timing reference signal includes determining a change in amplitude of the optical emission within a selected sample duration window exceeds a selected set point.

11. The method of claim 10, wherein the selected sample duration window is offset a selected amplitude from a pretrigger average amplitude.

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

13. The method of claim 10, wherein determining the timing of the change in state of the optical emission received in the optical sensor includes selecting a sample window duration for determining the timing of the change in state of the optical emission.

14. The method of claim 10, wherein the set of amplitude statistics includes determining a change in amplitude of the optical emission a plurality of times within a selected sample duration window.

15. The method of claim 10, wherein the set of amplitude statistics includes:

subdividing at least one phase of a timing reference signal into a plurality of subdivisions;

determining an amplitude statistic of the output optical sensor signal for each of the subdivisions; and

storing the amplitude statistic of the output optical sensor signal for each of the subdivisions.