Method and apparatus for pulsed plasma processing using a time resolved tuning scheme for RF power delivery

• US 8,264,154 B2
• Filed: 05/13/2009
• Issued: 09/11/2012
• Est. Priority Date: 05/14/2008
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Todorow, Valentin, Ramaswamy, Kartik, Banner, Samer
• Primary Examiner(s): CRAWFORD, JASON
• Application Number:
  US12/465,319
• Publication Number:
  US 20090284156A1
• Time in Patent Office: 1,217 Days
• Field of Search: 315/34, 315/111.21, 315/111.71, 315/160, 315310-311, 315/326, 315/344, 315/348, 315/360, 307/43, 333/17.1, 333/17.3, 333/99.PL
• US Class Current: 315/111.71
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/32146 Amplitude modulation, includes pulsing
• CPC Class Codes: H01J 37/32155 Frequency modulation
• CPC Class Codes: H01J 37/32174 Circuits specially adapted for controlling the RF discharge

Abstract

Embodiments of the present invention generally provide methods and apparatus for pulsed plasma processing over a wide process window. In some embodiments, an apparatus may include an RF power supply having frequency tuning and a matching network coupled to the RF power supply that share a common sensor for reading reflected RF power reflected back to the RF power supply. In some embodiments, an apparatus may include an RF power supply having frequency tuning and a matching network coupled to the RF power supply that share a common sensor for reading reflected RF power reflected back to the RF power supply and a common controller for tuning each of the RF power supply and the matching network.

Claims

1. An apparatus, comprising:

a first RF power supply having frequency tuning;

a first matching network coupled to the first RF power supply; and

a first common sensor for reading a reflected RF power reflected back to the first RF power supply and for providing a signal indicative of the reflected RF power to tune the first RF power supply and the first matching network.

2. The apparatus of claim 1, further comprising:

a controller for tuning the first RF power supply and the first matching network based upon the reading from the first common sensor.

3. The apparatus of claim 2, wherein the first matching network is embedded within the first RF power supply, and wherein the controller controls both tuning of the first matching network as well as a frequency with an RF cycle based on a common reading provided by the first common sensor as measured at an output of the first RF power supply.

4. The apparatus of claim 1, further comprising:

a process chamber having an antenna assembly disposed proximate a lid of the process chamber and a cathode pedestal for supporting a substrate to be processed, wherein the first RF power supply is coupled to the antenna assembly; and

a second RF power supply having frequency tuning coupled to the cathode pedestal, a second matching network coupled to second RF power supply, and a second common sensor for reading reflected RF power reflected back to the second RF power supply, the second common sensor coupled to the second RF power supply and the second matching network.

5. The apparatus of claim 4, further comprising:

a controller for tuning the first RF power supply and the first matching network based upon the reading from the first common sensor and for tuning the second RF power supply and the second matching network based upon the reading from the second common sensor.

6. The apparatus of claim 5:

wherein the first matching network is embedded within the first RF power supply and the controller controls both tuning of the first matching network as well as a frequency with an RF cycle of the first RF power supply based on a common reading provided by the first common sensor as measured at an output of the first RF power supply; and

wherein the second matching network is embedded within the second RF power supply and the controller controls both tuning of the second matching network as well as a frequency with an RF cycle of the second RF power supply based on a common reading provided by the second common sensor as measured at an output of the second RF power supply.

7. The apparatus of claim 4, further comprising:

a link coupling the first RF power supply and the second RF power supply to facilitate synchronizing the operation of one RF power supply to the other.

8. The apparatus of claim 7, wherein the first RF power supply and the second RF power supply are configured to operate in perfect synchronization or in a desired phase difference.

9. The apparatus of claim 4, wherein the first RF power supply and the second RF power supply can operate in a pulse mode having a pulse frequency of between about 100 Hz to about 100 kHz.

10. The apparatus of claim 4, wherein the first RF power supply and the second RF power supply can operate at a duty cycle of between about 10 to about 90 percent.

11. A method for tuning a system operating a plasma process using a source RF power supply and a bias RF power supply, each capable of frequency tuning and respectively coupled to a process chamber via a source matching network and a bias matching network, the method comprising:

igniting a plasma in a process chamber using the source RF power supply and the bias RF power supply, each set in a continuous wave mode and in a fixed frequency mode, with the source matching network and the bias matching network each set in an automatic tuning mode;

changing the source matching network to hold mode while keeping the bias matching network in automatic mode after the matching networks adjust to reduce reflected power from both the source and the bias RF power supplies;

turning on frequency tuning for the source RF power supply while keeping it off for the bias RF power supply;

turning on a pulsing mode for the source RF power supply and/or the bias RF power supply; and

placing the bias RF power supply in frequency tuning mode.

12. The method of claim 11, further comprising:

returning the source matching network to automatic mode after placing the bias RF power supply in frequency tuning mode.

13. The method of claim 11, wherein the source RF power supply and the bias RF power supply are in a master/slave arrangement to provide synchronized or embedded synchronized pulsing.

14. The method of claim 11, wherein the source RF power supply and the bias RF power supply are each in a master mode to operate the source RF power supply in pulsing mode with the bias RF power supply in continuous wave mode or the bias RF power supply in pulsing mode with the source RF power supply in continuous wave mode.

15. A method for tuning a system operating a plasma process using a source RF power supply and a bias RF power supply, each capable of frequency tuning and respectively coupled to a process chamber via a source matching network and a bias matching network, the method comprising:

(a) forming a plasma in a process chamber by providing RF power from the source RF power supply and/or the bias RF power supply at a desired pulsing frequency and an initial duty cycle of between about 85 to about 95 percent in frequency tuning mode with the source matching network and the bias matching network in automatic tuning mode; and

(b) while the source RF power supply and the bias RF power supply are still on, changing the initial duty cycle to a desired duty cycle after the matching networks adjust to reduce reflected power from both the source and the bias RF power supplies.

16. The method of claim 15, wherein the initial duty cycle is about 90 percent.

17. The method of claim 15, further comprising:

(c) switching the matching networks into hold mode after changing the initial duty cycle to a desired duty cycle.

18. The method of claim 15, further comprising:

(c) switching the matching networks into hold mode after the matching networks adjust to reduce reflected power from both the source and the bias RF power supplies but prior to changing the initial duty cycle to a desired duty cycle.

19. The method of claim 15, wherein the source RF power supply and the bias RF power supply are in a master/slave arrangement to provide synchronized or embedded synchronized pulsing.

20. The method of claim 15, wherein the source RF power supply and the bias RF power supply are each in a master mode to operate the source RF power supply in pulsing mode with the bias RF power supply in continuous wave mode or the bias RF power supply in pulsing mode with the source RF power supply in continuous wave mode.

21. A method for tuning a system operating a plasma process in a time resolved manner using a source RF power supply and a bias RF power supply, each capable of frequency tuning and respectively coupled to a process chamber via a source matching network and a bias matching network, the method comprising:

igniting a plasma in a process chamber using the source RF power supply and the bias RF power supply, each independently set in a first operational mode selected from either a continuous wave mode or a pulsing mode and in a first tuning mode selected from either a fixed frequency mode or a frequency tuning mode, with the source matching network and the bias matching network each independently set in a first match mode selected from either an automatic tuning mode or a hold mode;

upon expiration of a first period of time, switching the first operational mode of one or both of the source RF power supply and the bias RF power supply;

upon expiration of a second period of time, switching the first tuning mode of one or both of the source RF power supply and the bias RF power supply; and

upon expiration of a third period of time, switching the first match mode of one or both of the source matching network and the bias matching network;

wherein the first, second, and third periods of time are selected to reduce a reflected power reflected back to the source RF power supply and the bias RF power supply.