Automatic impedance tuning with RF dual level pulsing

Patent metadata

Field	Value
Publication number	US-9614524-B1
Application number	US-201615007818-A
Country	US
Kind code	B1
Filing date	Jan 27, 2016
Priority date	Nov 28, 2015
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

Methods and systems for RF pulse reflection reduction are provided herein. In some embodiments, a method includes (a) providing a plurality of pulsed RF power waveforms from a plurality of RF generators to a process chamber during a first duty cycle, (b) measuring a first power level impedance Z 1 and a different second power level impedance Z 2 at different time periods during the first duty cycle, (c) adjusting the second power level impedance Z2 towards 50 ohm such that a standing wave ratio (SWR) of the second power level impedance Z2 decreases towards 50 ohm and a SWR of the first power level impedance Z1 increases from 50 ohm, and (e) repeating (d) until the SWR of the first power level impedance Z 1 is substantially equal to the SWR of the second power level impedance Z 2 .

First claim

The invention claimed is:

1. A method comprising:
(a) providing a plurality of pulsed RF power waveforms from a plurality of RF generators to a process chamber during a first duty cycle, and providing a pulse switch timing signal from one of the plurality of RF generators to synchronize the plurality of pulsed RF power waveforms from the plurality of RF generators;
(b) measuring a first power level impedance Z 1 and a different second power level impedance Z 2 at different time periods during the first duty cycle;
(c) adjusting the first power level impedance Z 1 to 50 ohm;
(d) further adjusting the first power level impedance Z 1 such that a standing wave ratio (SWR) of the first power level impedance Z 1 increases from 50 ohm, and adjusting the second power level impedance Z 2 such that a SWR of the second power level impedance Z 2 decreases; and
(e) repeating (d) until the SWR of the first power level impedance Z 1 is substantially equal to the SWR of the second power level impedance Z 2 .

2. The method of claim 1 , wherein the pulse switch timing signal is a 13 MHz on/off timing signal.

3. The method of claim 1 , wherein at least one of the plurality of pulsed RF power waveforms is a dual level pulsing (DLP) waveform pulsed at multiple power levels.

4. The method of claim 1 , wherein the first power level impedance Z 1 is higher than the second power level impedance Z 2 .

5. The method of claim 1 , wherein the first power level impedance Z 1 and the second power level impedance Z 2 are measured using a voltage/current measuring device.

6. The method of claim 1 , wherein the first power level impedance Z 1 is a combined impendence of all the plurality of pulsed RF power waveforms during a first time period of the duty cycle, and wherein the second power level impedance Z 2 is a combined impendence of all the plurality of pulsed RF power waveforms during a second time period of the duty cycle.

7. The method of claim 6 , wherein the first power level impedance Z 1 and second power level impedance Z 2 include the impedance produced by a pulse switch timing signal provided by one of the plurality of RF generators to synchronize the plurality of pulsed RF power waveforms from the plurality of RF generators.

8. The method of claim 6 , further comprising:
measuring a third power level impedance Z 3 at a third time period during the first duty cycle;
adjusting the third power level impedance Z 3 such that a SWR of the third power level impedance Z 3 decreases; and
repeat (d) until the SWR of the first power level impedance Z 1 is substantially equal to the SWR of the second power level impedance Z 2 and the third power level impedance Z 3 .

9. The method of claim 1 , wherein the SWR of the first power level impedance Z 1 is determined to be substantially equal to the SWR of the second power level impedance Z 2 when the first power level impedance Z 1 is within a threshold range of the SWR of the second power level impedance Z 2 .

10. The method of claim 9 , wherein the threshold is a predetermined percentage of a radius of the SWR for Z 1 and Z 2 .

11. The method of claim 1 , wherein the first power level impedance Z 1 and the second power level impedance Z 2 are adjusted using a match network.

12. A non-transitory computer readable medium having instructions stored thereon that, when executed, cause a method of operating a plasma enhanced substrate processing system using multi-level pulsed RF power to be performed, the method comprising:
(a) providing a plurality of pulsed RF power waveforms from a plurality of RF generators to a process chamber during a first duty cycle, and providing a pulse switch timing signal from one of the plurality of RF generators to synchronize the plurality of pulsed RF power waveforms from the plurality of RF generators;
(b) measuring a first power level impedance Z 1 and a different second power level impedance Z 2 at different time periods during the first duty cycle;
(c) adjusting the first power level impedance Z 1 to 50 ohm;
(d) further adjusting the first power level impedance Z 1 such that a standing wave ratio (SWR) of the first power level impedance Z 1 increases from 50 ohm, and adjusting the second power level impedance Z 2 such that a SWR of the second power level impedance Z 2 decreases; and
(e) repeating (d) until the SWR of the first power level impedance Z 1 is substantially equal to the SWR of the second power level impedance Z 2 .

13. The non-transitory computer readable medium of claim 12 , wherein the pulse switch timing signal is a 13 MHz on/off timing signal.

14. The non-transitory computer readable medium of claim 12 , wherein at least one of the plurality of pulsed RF power waveforms is a dual level pulsing (DLP) waveform pulsed at multiple power levels.

15. The non-transitory computer readable medium of claim 12 , wherein the SWR of the first power level impedance Z 1 is determined to be substantially equal to the SWR of the second power level impedance Z 2 when the first power level impedance Z 1 is within a threshold range of the SWR of the second power level impedance Z 2 .

16. The non-transitory computer readable medium of claim 15 , wherein the threshold is a predetermined percentage of a radius of the SWR for Z 1 and Z 2 .

17. A substrate processing system comprising:
a plurality of RF generators configured to provide a plurality of pulsed RF power waveforms to a process chamber during a first duty cycle, wherein at least one of the plurality of RF generators is configured to provide a pulse switch timing signal to the other the RF generators to synchronize the plurality of pulsed RF power waveforms from the plurality of RF generators;
at least one voltage/current measuring device configured to measure reflected power for the plurality of pulsed RF power waveforms; and
one or more match networks each coupled to one of the plurality of RF generators, wherein each of the one or more match networks is configured to:
(a) adjust a first power level impedance Z 1 to 50 ohm;
(b) further adjust the first power level impedance Z 1 such that a standing wave ratio (SWR) of the first power level impedance Z 1 increases from 50 ohm, and adjust a second power level impedance Z 2 such that a SWR of the second power level impedance Z 2 decreases; and

(c) repeat (b) until the SWR of the first power level impedance Z 1 is substantially equal to the SWR of the second power level impedance Z 2 is configured to:
(a) adjust a first power level impedance Z 1 to 50 ohm;
(b) further adjust the first power level impedance Z 1 such that a standing wave ratio (SWR) of the first power level impedance Z 1 increases from 50 ohm, and adjust a the second power level impedance Z 2 such that a SWR of the second power level impedance Z 2 decreases; and
(c) repeat (b) until the SWR of the first power level impedance Z 1 is substantially equal to the SWR of the second power level impedance Z 2 .

Assignees

• Applied Materials Inc

Inventors

• Kawasaki Katsumasa

Classifications

• H01J2237/334

  Etching · CPC title

• H03K19/0005 Primary

  Modifications of input or output impedance · CPC title

• G01R27/02

  Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant (by measuring phase angle only G01R25/00) · CPC title

• H01J37/32082

  Radio frequency generated discharge (H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence) · CPC title

• H01J37/32917

  Plasma diagnostics · CPC title