Edge Ramping

• US 20140076713A1
• Filed: 10/24/2012
• Published: 03/20/2014
• Est. Priority Date: 09/14/2012
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: John C. Valcore, Jr.
• Inventors: Valcore, John C. Jr., Lyndaker, Bradford J., Fong, Andrew S.
• Granted Patent: US 9,408,288 B2
• Time in Patent Office: Days
• US Class Current: 204/164
• CPC Class Codes: H01J 37/32165 Plural frequencies
• CPC Class Codes: H01J 37/32174 Circuits specially adapted for controlling the RF discharge
• CPC Class Codes: H01J 37/32183 Matching circuits
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence
• CPC Class Codes: H05H 2242/26 Matching networks

Abstract

Systems and methods for performing edge ramping are described. A system includes a base RF generator for generating a first RF signal. The first RF signal transitions from one state to another. The transition from one state to another of the first RF signal results in a change in plasma impedance. The system further includes a secondary RF generator for generating a second RF signal. The second RF signal transitions from one state to another to stabilize the change in the plasma impedance. The system includes a controller coupled to the secondary RF generator. The controller is used for providing parameter values to the secondary RF generator to perform edge ramping of the second RF signal when the second RF signal transitions from one state to another.

Claims

1. A system comprising:

a base RF generator for generating a first RF signal, wherein the first RF signal transitions from one state to another, the transition from one state to another of the first RF signal resulting in a change in plasma impedance;

a secondary RF generator for generating a second RF signal, wherein the second RF signal transitions from one state to another to stabilize the change in the plasma impedance;

a controller coupled to the secondary RF generator, the controller for providing parameter values to the secondary RF generator to perform edge ramping of the second RF signal when the second RF signal transitions from one state to another.

2. The system of claim 1, wherein the edge ramping has a positive or a negative slope.

3. The system of claim 1, wherein the parameter values include frequency values, power values, or a combination thereof.

4. A system for reducing an effect of a change in power level of a radio frequency (RF) signal on plasma impedance, comprising:

a primary generator including;

a primary driver and amplifier for generating a primary RF signal;

a primary digital signal processor (DSP) for identifying states of a digital pulsed signal, the states including a first state and a second state,

the primary DSP for identifying a first primary frequency input when the digital pulsed signal is in the first state and for identifying a second primary frequency input when the digital pulsed signal is in the second state;

a first primary auto frequency tuner (AFT) coupled to the primary DSP and the primary driver and amplifier, the first primary AFT for receiving the first primary frequency input from the primary DSP and tuning the primary RF signal to achieve plasma impedance corresponding to the first primary frequency input;

a second primary AFT coupled to the primary DSP and the primary driver and amplifier, the second primary AFT for receiving the second primary frequency input from the primary DSP and tuning the primary RF signal to achieve plasma impedance corresponding to the second primary frequency input,

the primary RF signal having a primary rate of transition from the first primary frequency input to the second primary frequency input;

a secondary generator including;

a secondary driver and amplifier for generating a secondary RF signal;

a secondary digital signal processor (DSP) for identifying the states of the digital pulsed signal,

the secondary DSP for identifying a first secondary frequency input when the digital pulsed signal is in the first state and for identifying a second secondary frequency input when the digital pulsed signal is in the second state;

a first secondary AFT coupled to the secondary DSP and the secondary driver and amplifier, the first secondary AFT for receiving the first secondary frequency input from the secondary DSP and tuning the secondary RF signal to achieve plasma impedance corresponding to the first secondary frequency input;

a second secondary AFT coupled to the secondary DSP and the secondary driver and amplifier, the second secondary AFT for receiving the second secondary frequency input from the secondary DSP and tuning the secondary RF signal to achieve plasma impedance corresponding to the second secondary frequency input,

the secondary DSP configured to determine a secondary rate of transition from the first secondary frequency input to the second secondary frequency input, wherein the secondary rate of transition is different than the primary rate of transition.

5. The system of claim 4, wherein the secondary rate of transition is less than the primary rate of transition.

6. The system of claim 4, wherein a first amount of time taken to transition from the first secondary frequency input to the second secondary frequency input is greater than a second amount of time taken to transition from the first primary frequency input to the second primary frequency input.

7. The system of claim 6, wherein the first amount of time is less than a third amount of time for plasma impedance to stabilize.

8. The system of claim 6, wherein the first amount of time is less than a third amount of time for an impedance matching circuit to match impedance of one or more portions of the secondary RF generator with impedance of one or more portions of a plasma chamber.

9. The system of claim 4, wherein the first state is a high state and the second state is a low state.

10. The system of claim 4, wherein the first state is an on state and the second state is an off state.

11. A system for reducing an effect of a change in power level of a radio frequency (RF) signal on plasma impedance, comprising:

a primary generator including;

a primary driver and amplifier for generating a primary RF signal;

one or more primary controllers coupled to the primary driver and amplifier, the one or more primary controllers configured to;

identify states of the digital pulsed signal, the states including a first state and a second state,

tune the primary RF signal to achieve plasma impedance corresponding to a first primary power input when the digital pulsed signal is in the first state; and

tune the primary RF signal to achieve plasma impedance corresponding to a second primary power input when the digital pulsed signal is in the second state,

the primary RF signal having a primary rate of transition from the first primary power input to the second primary power input;

a secondary generator including;

a secondary driver and amplifier for generating a secondary RF signal;

one or more secondary controllers coupled to the secondary driver and amplifier, the one or more secondary controllers configured to;

tune the secondary RF signal to achieve plasma impedance corresponding to a first secondary power input when the digital pulsed signal is in the first state;

tune the secondary RF signal to achieve plasma impedance corresponding to a second secondary power input when the digital pulsed signal is in the second state; and

determine a secondary rate of transition from the first secondary power input to the second secondary power input, wherein the secondary rate of transition is different than the primary rate of transition.

12. The system of claim 11, wherein the secondary rate of transition is less than the primary rate of transition.

13. The system of claim 11, wherein a first amount of time taken to transition from the first secondary power input to the second secondary power input is greater than a second amount of time taken to transition from the first primary power input to the second primary power input.

14. The system of claim 13, wherein the first amount of time is less than a third amount of time for plasma impedance to stabilize at the second state.

15. The system of claim 13, wherein the first amount of time is less than a third amount of time for an impedance matching circuit to match impedance of one or more portions of the secondary generator with impedance of one or more portions of a plasma chamber.

16. The system of claim 11, wherein the first state is a high state and the second state is a low state.

17. The system of claim 11, wherein the first state is an on state and the second state is an off state.

18. A method for reducing an effect of a change in power level of a radio frequency (RF) signal on plasma impedance, comprising:

identifying states of a digital pulsed signal, the states including a first state and a second state,

identifying a first primary frequency input when the digital pulsed signal is in the first state;

identifying a second primary frequency input when the digital pulsed signal is in the second state;

tuning a primary RF signal to achieve plasma impedance corresponding to the first primary frequency input when the digital pulsed signal is in the first state;

tuning the primary RF signal to achieve plasma impedance corresponding to the second primary frequency input when the digital pulsed signal is in the second state,

the primary RF signal having a primary rate of transition from the first primary frequency input to the second primary frequency input;

identifying a first secondary frequency input when the digital pulsed signal is in the first state;

identifying a second secondary frequency input when the digital pulsed signal is in the second state;

tuning a secondary RF signal to achieve plasma impedance corresponding to the first secondary frequency input when the digital pulsed signal is in the first state;

tuning the secondary RF signal to achieve plasma impedance corresponding to the second secondary frequency input when the digital pulsed signal is in the second state,

determining a secondary rate of transition from the first secondary frequency input to the second secondary frequency input, wherein the secondary rate of transition is different than the primary rate of transition.

19. The method of claim 18, wherein the secondary rate of transition is less than the primary rate of transition.

20. The method of claim 18, wherein a first amount of time taken to transition from the first secondary frequency input to the second secondary frequency input is greater than a second amount of time taken to transition from the first primary frequency input to the second primary frequency input.

21. The method of claim 20, wherein the first amount of time is less than a third amount of time for plasma impedance to stabilize at the second state.

22. The method of claim 20, wherein the first amount of time is less than a third amount of time, the third amount of time for matching impedance of one or more portions of the secondary generator with impedance of one or more portions of a plasma chamber.

23. The method of claim 20, wherein the first state is a high state and the second state is a low state.