Methods and apparatus for controlling plasma in a plasma processing system

• US 10,032,605 B2
• Filed: 07/06/2015
• Issued: 07/24/2018
• Est. Priority Date: 02/22/2012
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Valcore, Jr., John C., Lyndaker, Bradford J.
• Primary Examiner(s): Deo, Duy
• Assistant Examiner(s): Dahimene, Mahmoud
• Application Number:
  US14/792,527
• Publication Number:
  US 20150311041A1
• Time in Patent Office: 1,114 Days
• CPC Class Codes: B44C 1/22 Removing surface-material, e.g. by engraving, by etching for multi-layer articles B44C3/005
• CPC Class Codes: H01J 37/32091 the radio frequency energy being capacitively coupled to the plasma
• CPC Class Codes: H01J 37/32165 Plural frequencies
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H03L 5/00 Automatic control of voltage, current, or power
• CPC Class Codes: H05H 2242/26 Matching networks

Abstract

Methods and apparatus for processing a substrate in a multi-frequency plasma processing chamber are disclosed. The base RF signal pulses between a high power level and a low power level. Each of the non-base RF generators, responsive to a control signal, proactively switches between a first predefined power level and a second predefined power level as the base RF signal pulses. Alternatively or additionally, each of the non-base RF generators, responsive to a control signal, proactively switches between a first predefined RF frequency and a second predefined RF frequency as the base RF signal pulses. Techniques are disclosed for ascertaining in advance of production time the first and second predefined power levels and/or the first and second predefined RF frequencies for the non-base RF signals.

Claims

1. A method for processing a substrate, comprising:

controlling a base radio frequency (RF) generator to generate a base RF signal that pulses between a first base power level and a second base power level; and

synchronizing a non-base RF generator with the base RF generator to generate a non-base RF signal that pulses between a first pre-determined non-base power level and a second pre-determined non-base power level,

wherein to synchronize the pulsing of the non-base RF signal with the pulsing of the base RF signal, the non-base RF signal is pulsed to achieve the first pre-determined non-base power level simultaneous with achievement of the first base power level and to achieve the second pre-determined non-base power level simultaneous with achievement of the second base power level,

wherein to synchronize the pulsing of the non-base RF signal with the pulsing of the base RF signal, both the base RF generator and the non-base RF generator are coupled to one and a same electrode of a plasma chamber via an impedance matching network and another electrode of the plasma chamber is coupled to a ground potential, wherein the other electrode faces the electrode, and the substrate is located over the electrode,

wherein the first pre-determined non-base power level and the second pre-determined non-base power level are achieved during the processing of the substrate without detection of changes in plasma impedance during the processing of the substrate,

wherein each of the first pre-determined non-base power level and the second pre-determined non-base power level is configured to reduce a change in the plasma impedance caused by said pulsing of the base RF signal.

2. The method of claim 1, wherein the first base power level is a pre-determined power level and the second base power level is a pre-determined power level.

3. The method of claim 1, wherein the base RF generator is a 2 megahertz (MHz) RF generator and the non-base RF generator is a 27 MHz or a 60 MHz RF generator.

4. The method of claim 1, wherein the first base power level includes a range of power values of the base RF signal and the range of power values is exclusive of a range of power values of the second base power level of the base RF signal.

5. The method of claim 1, wherein the first pre-determined non-base power level facilitates achievement of a process result and the second pre-determined non-base power level facilitates achievement of another process result.

6. The method of claim 1, wherein synchronizing the non-base RF generator comprises sending a control signal to the non-base RF generator to facilitate a generation of the first pre-determined non-base power level with the generation of the first base power level and a generation of the second pre-determined non-base power level with the generation of the second base power level.

7. The method of claim 1, wherein synchronizing the non-base RF generator comprises:

sending a control signal to the non-base RF generator to achieve the second pre-determined non-base power level without detecting a change in the plasma impedance caused by a transition from the first base power level to the second base power level wherein the control signal is sent to the non-base RF generator to achieve the first pre-determined non-base power level without detecting a change in the plasma impedance caused by a transition from the second base power level to the first base power level.

8. The method of claim 1, further comprising calculating the first pre-determined non-base power level and the second pre-determined non-base power level when a pre-determined measurement of a plasma parameter associated with plasma within the plasma chamber is achieved, wherein the pre-determined measurement of the plasma parameter is achieved when a process parameter associated with a substrate within the plasma chamber is achieved.

9. The method of claim 8, wherein calculating the first pre-determined non-base power level and the second pre-determined non-base power level is performed before said controlling the base RF generator to generate the base RF signal and said synchronizing the non-base RF generator with the base RF generator to generate the non-base RF signal that pulses between the first pre-determined non-base power level and the second pre-determined non-base power level.

10. The method of claim 1, further comprising:

calculating the first pre-determined non-base power level and the second pre-determined non-base power level from a measurement of a plasma parameter associated with plasma within the plasma chamber.

11. The method of claim 10, wherein calculating the first pre-determined non-base power level and the second pre-determined non-base power level is performed before said controlling the base RF signal to generate the base RF signal and said synchronizing the non-base RF generator to generate the non-base RF signal that pulses between the first pre-determined non-base power level and the second pre-determined non-base power level.

12. A method for processing a substrate, comprising:

controlling a base radio frequency (RF) generator to generate a base RF signal that pulses between a first base power level and a second base power level; and

synchronizing a non-base RF generator to generate a non-base RF signal that pulses between a first pre-determined non-base frequency and a second pre-determined non-base frequency,

wherein to synchronize the pulsing of the non-base RF signal with the pulsing of the base RF signal, the non-base RF signal is pulsed to achieve the first pre-determined non-base frequency simultaneous with achievement of the first base power level and to achieve the second pre-determined non-base frequency simultaneous with achievement of the second base power level,

wherein to synchronize the pulsing of the non-base RF signal with the pulsing of the base RF signal, the base RF generator and the non-base RF generator are coupled to one and a same electrode of a plasma chamber via an impedance matching network and another electrode of the plasma chamber is coupled to a ground potential, wherein the other electrode faces the electrode, and the substrate is located over the electrode,

wherein the first pre-determined non-base frequency and the second pre-determined non-base frequency are achieved during the processing of the substrate without detection of changes in plasma impedance during the processing of the substrate.

13. The method of claim 12, wherein the first base power level includes a range of power values of the base RF signal and the range of power values is exclusive of a range of power values of the second base power level of the base RF signal.

14. The method of claim 12, wherein synchronizing the non-base RF generator comprises:

sending a control signal to the non-base RF generator to achieve the second pre-determined non-base frequency without detecting a change in the plasma impedance caused by a transition from the first base power level to the second base power level, wherein the control signal is sent to the non-base RF generator to achieve the first pre-determined non-base frequency without detecting a change in the plasma impedance caused by a transition from the second base power level to the first base power level.

15. The method of claim 12, further comprising:

calculating the first pre-determined non-base frequency and the second pre-determined non-base frequency from a measurement of a plasma parameter associated with plasma within the plasma chamber.

16. The method of claim 15, wherein calculating the first pre-determined non-base frequency and the second pre-determined non-base frequency is performed before said controlling the base RF signal to generate the base RF signal and said synchronizing the non-base RF generator to generate the non-base RF signal that pulses between the first pre-determined non-base frequency and the second pre-determined non-base frequency.

17. The method of claim 12, further comprising calculating the first pre-determined non-base frequency and the second pre-determined non-base frequency when a pre-determined measurement of a plasma parameter associated with plasma within the plasma chamber is achieved, wherein the pre-determined measurement of the plasma parameter is achieved when a process parameter associated with a substrate within the plasma chamber is achieved.

18. The method of claim 17, wherein calculating the first pre-determined non-base frequency and the second pre-determined non-base frequency is performed before said controlling the base RF generator to generate the base RF signal and said synchronizing the non-base RF generator to generate the non-base RF signal that pulses between the first pre-determined non-base frequency and the second pre-determined non-base frequency.

19. A method for processing a substrate, comprising:

generating by a base radio frequency (RF) generator a base RF signal that pulses at a pulsing frequency between a first base power level and a second base power level;

providing a control signal having the pulsing frequency to a non-base RF generator; and

generating by the non-base RF generator, a non-base RF signal upon receiving the control signal, wherein the non-base RF signal pulses between a first non-base pre-determined parameter level and a second non-base pre-determined parameter level, wherein the non-base RF signal is pulsed to achieve the first non-base pre-determined parameter level simultaneous with achievement of the first base power level and to achieve the second non-base pre-determined parameter level simultaneous with achievement of the second base power level,

wherein to achieve the first non-base pre-determined parameter level simultaneous with the achievement of the first base power level and to achieve the second non-base pre-determined parameter level simultaneous with the achievement of the second base power level, the RF generator and the non-base RF generator are configured to be coupled to one and a same electrode of a plasma chamber via an impedance matching circuit and another electrode of the plasma chamber is coupled to a ground potential, wherein the other electrode faces the electrode, and the substrate is located over the electrode,

wherein the first non-base pre-determined parameter level and the second non-base pre-determined parameter level are achieved during the processing of the substrate without detection of changes in plasma impedance during the processing of the substrate,

wherein each of the first non-base pre-determined parameter level and the second non-base pre-determined parameter level is configured to reduce a change in the plasma impedance caused by the pulsing of the base RF signal.

20. The method of claim 19, wherein providing the control signal comprises:

sending the control signal to the non-base RF generator to achieve the second non-base pre-determined parameter level without detecting a change in the plasma impedance caused by a transition from the first base power level to the second base power level; and

sending the control signal to the non-base RF generator to achieve the first non-base pre-determined parameter level without detecting a change in the plasma impedance caused by a transition from the second base power level to the first base power level.