Frequency tuning for pulsed radio frequency plasma processing

Patent metadata

Field	Value
Publication number	US-9711331-B2
Application number	US-201715403021-A
Country	US
Kind code	B2
Filing date	Jan 10, 2017
Priority date	Jun 30, 2014
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

This disclosure describes systems, methods, and apparatus for pulsed RF power delivery to a plasma load for plasma processing of a substrate. In order to maximize power delivery, a calibration phase using a dummy substrate or no substrate in the chamber, is used to ascertain a preferred fixed initial RF frequency for each pulse. This fixed initial RF frequency is then used at the start of each pulse during a processing phase, where a real substrate is used and processed in the chamber.

First claim

What is claimed is:

1. A method comprising:
providing pulsed RF power to a plasma load, where each pulse comprises RF power having a controllable frequency;
tuning an initial RF frequency for each pulse in a string of pulses, in a calibration phase, by reducing a difference between a characteristic indicative of the pulsed RF power and a desired characteristic of the pulsed RF power, at a start of consecutive pulses, until the difference is below a threshold; then
selecting the initial RF frequency as a fixed initial RF frequency for use in a processing phase using a substrate different than a substrate used during the calibration run; and
tuning the RF frequency during the processing phase within each pulse but returning to the fixed initial RF frequency at a start of each pulse.

2. The method of claim 1 , wherein the characteristic indicative of the pulsed RF power is reflected power.

3. The method of claim 1 , wherein the characteristic indicative of the pulsed RF power is load impedance power.

4. The method of claim 1 , wherein the characteristic indicative of the pulsed RF power is a density of the plasma.

5. A non-transitory, tangible computer readable storage medium, encoded with processor readable instructions to perform a method for frequency tuning, the method comprising:
in a calibration phase,
tuning an initial RF frequency at a start of each pulse in a string of RF pulses, until a difference between a characteristic indicative of power and a desired characteristic of the power at the start of two consecutive pulses in the string, is below a threshold; then
selecting the initial RF frequency as a fixed initial RF frequency to be used during a processing phase; and

in the processing phase,
setting an initial RF frequency for all pulses in the processing phase equal to the fixed initial RF frequency selected during the calibration phase; and
tuning the RF frequency during each pulse, but returning to the fixed initial RF frequency at a start of each pulse.

6. The non-transitory, tangible computer readable storage medium of claim 5 , wherein the characteristic indicative of power is reflected power.

7. The non-transitory, tangible computer readable storage medium of claim 5 , wherein the characteristic indicative of power is load impedance power.

8. The non-transitory, tangible computer readable storage medium of claim 5 , wherein the characteristic indicative of power is a density of the plasma.

9. A power delivery system comprising:
a power source configured to provide pulsed RF power to a plasma load;
a sensor configured to sample a characteristic indicative of the pulsed RF power;
a controller in communication with the sensor and the power source and executable to:
in a calibration phase,
tune an initial RF frequency at a start of each pulse in a string of RF pulses, until a difference between the characteristic indicative of the pulsed RF power and a desired characteristic of the power at the start of consecutive pulses in the string, is below a threshold; then
select the initial RF frequency as a fixed initial RF frequency to be used during a processing phase; and

in the processing phase,
set an initial RF frequency for all pulses in the processing phase equal to the fixed initial RF frequency selected during the calibration phase; and
tune the RF frequency of pulsed RF power during each pulse, but return to the fixed initial RF frequency at a start of each pulse.

10. The power delivery system of claim 9 , wherein the sensor is a reflected power sensor.

11. The power delivery system of claim 10 , wherein the sensor is a directional coupler.

12. The power delivery system of claim 9 , wherein the sensor is a delivered power sensor.

13. The power delivery system of claim 9 , wherein the sensor is an impedance sensor.

14. The power delivery system of claim 9 , wherein the sensor is a plasma density sensor.

15. The power delivery system of claim 9 , wherein the power source is in communication with a switching circuit that converts the RF power to the pulsed RF power.

16. The power delivery system of claim 9 , wherein the sensor is part of an oscilloscope.

17. The power delivery system of claim 9 , wherein the power source is configured to provide the pulsed RF power to a plasma load via a matching network.

Assignees

• Advanced Energy Ind Inc

Inventors

• Mueller Michael
• Choi Myeong Yeol

Classifications

• H05H1/46

  using applied electromagnetic fields, e.g. high frequency or microwave energy (H05H1/26 takes precedence) · CPC title

• H01J37/32935

  Monitoring and controlling tubes by information coming from the object and/or discharge · CPC title

• H01J37/32155 Primary

  Frequency modulation · CPC title

• H01J37/3299

  Feedback systems · CPC title

• H01J37/32146

  Amplitude modulation, includes pulsing · CPC title