Impedance-Based Adjustment of Power and Frequency

• US 20130214683A1
• Filed: 11/01/2012
• Published: 08/22/2013
• Est. Priority Date: 02/22/2012
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Valcore, John C. Jr., Lyndaker, Bradford J.
• Granted Patent: US 9,171,699 B2
• Time in Patent Office: Days
• US Class Current: 315/111.21
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32146 Amplitude modulation, includes pulsing
• 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: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32981 Gas analysis
• CPC Class Codes: H01J 37/3299 Feedback systems

Abstract

Systems and methods for impedance-based adjustment of power and frequency are described. A system includes a plasma chamber for containing plasma. The plasma chamber includes an electrode. The system includes a driver and amplifier coupled to the plasma chamber for providing a radio frequency (RF) signal to the electrode. The driver and amplifier is coupled to the plasma chamber via a transmission line. The system further includes a selector coupled to the driver and amplifier, a first auto frequency control (AFC) coupled to the selector, and a second AFC coupled to the selector. The selector is configured to select the first AFC or the second AFC based on values of current and voltage sensed on the transmission line.

Claims

1. A system comprising:

a plasma chamber for containing plasma, the plasma chamber including an electrode;

a driver and amplifier coupled to the plasma chamber for providing a radio frequency (RF) signal to the electrode, the driver and amplifier coupled to the plasma chamber via a transmission line;

a selector coupled to the driver and amplifier;

a first auto frequency control (AFC) coupled to the selector;

a second AFC coupled to the selector,

wherein the selector is configured to select the first AFC or the second AFC based on values of current and voltage sensed on the transmission line.

2. The system of claim 1, wherein the values of current and voltage are used to generate one or more values of gamma, wherein the selector is configured to select the first AFC when one of the values of gamma is greater than a first threshold and is configured to select the second AFC when another one of the values of gamma is greater than a second threshold.

3. The system of claim 1, wherein the selector includes a multiplexer.

4. A system comprising:

a primary generator coupled to an electrode, the primary generator including a primary driver and amplifier for supplying a primary radio frequency (RF) signal to the electrode, the primary generator further including a primary automatic frequency tuner (AFT) to provide a first primary frequency input to the primary driver and amplifier when a pulsed signal is in a first state, the primary AFT configured to provide a second primary frequency input to the primary driver and amplifier when the pulsed signal is in a second state; and

a secondary generator coupled to the electrode, the secondary generator including a secondary driver and amplifier for supplying a secondary RF signal to the electrode, the secondary generator further including a first secondary AFT coupled to the secondary driver and amplifier, the secondary generator including a second secondary AFT coupled to the secondary driver and amplifier, the secondary generator including a processor, the processor coupled to the first secondary AFT and the second secondary AFT, the secondary generator further including one or more sensors coupled to the electrode, the one or more sensors for sensing current and voltage transferred between the secondary generator and the electrode during the first and second states, the processor configured to generate parameters based on the current and voltage, the processor configured to determine whether a first one of the parameters for the first state exceeds a first boundary and whether a second one of the parameters for the second state exceeds a second boundary, the first secondary AFT configured to provide a first secondary frequency input to the secondary driver and amplifier upon receiving the determination that the first parameter exceeds the first boundary, the second secondary AFT configured to provide a second secondary frequency input to the secondary driver and amplifier upon receiving the determination that the second parameter exceeds the second boundary.

5. The system of claim 4, further comprising a selector coupled to the processor for selecting the first secondary AFT or the second secondary AFT, the selector for selecting the first secondary AFT in response to receiving a signal from the secondary processor indicating that the first parameter exceeds the first boundary, the selector for selecting the second secondary AFT in response to receiving a signal from the secondary processor indicating that the second parameter exceeds the second boundary.

6. The system of claim 4, wherein the electrode includes a lower electrode of a plasma chamber.

7. The system of claim 4, wherein during the first state, the primary driver and amplifier is configured to generate the primary RF signal having a lower frequency than that of the secondary RF signal, wherein the primary RF signal has a higher amount of power than the secondary RF signal.

8. The system of claim 4, wherein the processor is configured to determine whether the pulsed signal is in the first or the second state based on a magnitude of the pulsed signal.

9. The system of claim 4, wherein each of the first and second parameter includes a gamma value or an impedance difference value.

10. A system comprising:

a digital pulsing source for generating a pulsed signal;

a primary generator including;

a primary driver and amplifier coupled to an electrode for supplying a primary radio frequency (RF) signal to the electrode;

one or more primary processors coupled to the pulsing source for receiving the pulsed signal,

the one or more primary processors configured to;

identify a first one of two states of the pulsed signal and a second one of the two states;

determine to provide a primary power value to the primary driver and amplifier when the pulsed signal is in the first state; and

determine to provide a primary frequency value of the primary RF signal when the pulsed signal is in the first state; and

a secondary generator including;

a secondary driver and amplifier coupled to the electrode for supplying a secondary RF signal to the electrode;

one or more secondary processors coupled to the pulsing source for receiving the pulsed signal,

the one or more secondary processors configured to;

determine whether a parameter associated with plasma exceeds a first boundary when the pulsed signal is in the first state;

determine whether the parameter exceeds a second boundary when the pulsed signal is in the second state;

determine to provide a first secondary power value to the secondary driver and amplifier in response to determining that the parameter exceeds the first boundary;

determine to provide a second secondary power value to the secondary driver and amplifier in response to determining that the parameter exceeds the second boundary;

determine to provide a first secondary frequency value to the secondary driver and amplifier in response to determining that the parameter exceeds the first boundary; and

determine to provide a second secondary frequency value to the secondary driver and amplifier in response to determining that the parameter exceeds the second boundary.

11. The system of claim 10, further comprising a selector coupled to the one or more secondary processors for selecting the first secondary frequency value or the second secondary frequency value, the selector for selecting the first secondary frequency value in response to receiving a signal from the one or more secondary processors indicating that the first parameter exceeds the first boundary, the selector for selecting the second secondary frequency value in response to receiving a signal from the one or more secondary processors indicating that the second parameter exceeds the second boundary.

12. The system of claim 10, wherein the parameter includes a gamma value or an impedance difference value.

13. The system of claim 10, wherein the electrode includes a lower electrode of a plasma chamber.

14. The system of claim 10, wherein during the first state, the primary driver and amplifier is configured to generate the primary RF signal having a lower frequency than that of the secondary RF signal, wherein the primary RF signal has a higher amount of power than the secondary RF signal.

15. The system of claim 10, wherein each of the primary and secondary frequency values are tuned.

16. The system of claim 10, wherein the one or more primary processors determine whether the pulsed signal is in the first or the second state based on a magnitude of the pulsed signal.

17. A method comprising:

receiving a digital pulsing signal, the digital pulsing signal having two states;

receiving current and voltage values;

calculating parameters associated with plasma impedance from the current and voltage values;

determining during the first state whether a first one of the parameters exceeds a first boundary;

providing a first frequency value and a first power value to a radio frequency (RF) driver and amplifier upon determining that the first parameter exceeds the first boundary;

determining during the second state whether a second one of the parameters exceeds a second boundary; and

providing a second frequency value and a second power value to the RF driver and amplifier upon determining that the second parameter exceeds the second boundary.

18. The method of claim 17, wherein the method is used to process semiconductor wafers to make integrated circuits.

19. The method of claim 17, wherein the parameters include gamma values or impedance difference values.

20. The method of claim 17, further comprising selecting between providing the first frequency value and the first power value or the second frequency value and the second power value.