SYSTEMS AND METHODS FOR CALIBRATING A SWITCHED MODE ION ENERGY DISTRIBUTION SYSTEM

• US 20140062303A1
• Filed: 08/28/2012
• Published: 03/06/2014
• Est. Priority Date: 08/28/2012
• Status: Active Grant

• Current Assignee: AES Global Holdings Pte Ltd. (Advanced Energy Industries, Inc. (China))
• Original Assignee: Advanced Energy Industries Incorporated
• Inventors: Hoffman, Daniel J., Carter, Daniel, Brouk, Victor, Hattel, William J.
• Granted Patent: US 9,210,790 B2
• Time in Patent Office: Days
• US Class Current: 315/111.21
• CPC Class Codes: C23C 14/345 using substrate bias
• 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 37/32422 Arrangement for selecting ions or species in the plasma
• CPC Class Codes: H01J 37/32706 Polarising the substrate
• CPC Class Codes: H01J 37/32926 Software, data control or modelling
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/3299 Feedback systems
• CPC Class Codes: H05H 1/0081 by electric means
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence

Abstract

Systems, methods and apparatus for regulating ion energies and ion energy distributions along with calibrating a bias source and a plasma processing chamber are disclosed. An exemplary method includes applying a periodic voltage function to a load emulator, which emulates electrical characteristics of a plasma load and associated electronics such as an e-chuck. The load emulator can be measured for various electrical parameters and compared to expected parameters generated by the bias source. Differences between measured and expected values can be used to identify and correct faults and abnormalities in the bias supply, the chamber, or a power source used to ignite and sustain the plasma. Once the bias supply is calibrated, the chamber can be calibrated by measuring and calculating an effective capacitance comprising a series and parallel capacitance of the substrate support and optionally the substrate.

Claims

1. A method of calibrating a bias supply configured to generate a potential on a top surface of a substrate during plasma processing of the substrate, the method comprising:

receiving a modified periodic voltage function comprising pulses and a portion between the pulses;

receiving an expected ion energy;

receiving an expected ion current;

delivering the modified periodic voltage function to a plasma load emulator;

measuring a voltage across a sheath capacitance component of the plasma load emulator;

applying a known current from a current source of the plasma load emulator to the sheath capacitance component;

comparing the voltage across the sheath capacitance component to the expected ion energy and determining an ion energy error from this comparing;

comparing the current to the expected ion current and determining an ion current error from this comparing; and

reporting the ion energy error and the ion current error.

2. The method of claim 1, further comprising receiving an expected sheath capacitance, accessing a sheath capacitance of the sheath capacitance component, comparing the sheath capacitance to the expected sheath capacitance, determining a sheath capacitance error from the third comparing, and reporting the sheath capacitance error.

3. The method of claim 1, wherein the ion current error and the ion energy error are used to calibrate a bias supply that generates the modified periodic voltage function.

4. The method of claim 3, wherein the ion current error and the ion energy error are converted to calibration data, which a controller of the bias supply uses to periodically adjust its instructions for controlling the modified periodic voltage function.

5. The method of claim 1, wherein the ion energy error and the ion current error are calculated values.

6. The method of claim 1, wherein the ion energy error and the ion current error are measured values.

7. A system comprising:

a bias supply providing a modified periodic voltage, the bias supply comprising;

a power supply configured to provide a periodic voltage function;

an ion current compensation component configured to modify the periodic voltage function with an ion compensation current so that the bias supply provides the modified periodic voltage function; and

a controller configured to provide instructions to the power supply to adjust the periodic voltage function and to provide instructions to the ion current compensation component to adjust the ion compensation current;

a calibration component receiving the modified periodic voltage function, the calibration component comprising;

a load emulator having circuitry configured to emulate a plasma load, the load emulator further configured to receive the modified periodic voltage function;

a measurement component configured to make one or more measurements of the modified periodic voltage function as it interacts with the circuitry of the load emulator; and

an analysis component configured to determine an ion current error by comparing at least one measured value from the measurement component and at least one expected value from the bias supply.

8. The system of claim 7, wherein the ion current error is calculated as a difference between an expected ion current provided by the bias supply and a measured current provided by the measurement component, where the measured current is equivalent to an ion current.

9. The system of claim 8, wherein the load emulator includes a current source configured to emulate an ion current in a plasma load.

10. The system of claim 9, wherein the measured value equivalent to an ion current is an output current of the current source.

11. The system of claim 10, wherein the output current of the current source emulates an electrical characteristic of plasma density.

12. The system of claim 8, wherein the analysis component is further configured to determine an ion energy error by comparing at least one measured value from the measurement component and at least one expected value from the bias supply.

13. The system of claim 12, wherein the ion energy error is calculated as a difference between an expected ion energy provided by the bias supply and a measured value equivalent to an ion energy provided by the measurement component.

14. The system of claim 13, wherein the load emulator includes a sheath capacitance component configured to emulate a sheath capacitance in a plasma load.

15. The system of claim 14, wherein the measured value equivalent to the ion energy is the voltage across the sheath capacitance component.

16. The system of claim 8, wherein the load emulator further comprises an effective capacitance component configured to emulate an effective capacitance of a plasma load.

17. The system of claim 16, wherein the effective capacitance component is configured to emulate a capacitance of a substrate support and one or more stray capacitances.

18. The system of claim 7, wherein the load emulator further comprises a rectifying component configured to emulate rectifying effects of a plasma sheath.

19. The system of claim 18, wherein the rectifying component is arranged in parallel to the sheath capacitance component, and wherein the voltage across the sheath capacitance is also the voltage across the rectifying component.

20. The system of claim 7, further comprising a cable emulation component configured to emulate electrical characteristics of a power path that would be used to couple the modified periodic voltage function to a substrate support of a plasma load.

21. The system of claim 7, wherein the controller provides instructions to the power supply and the ion current compensation component based on the ion current error calculated by the analysis component.

22. A system comprising:

a bias supply generating a modified periodic voltage function, wherein the modified periodic voltage function comprises periodic pulses with a sloped portion between the pulses, wherein the slope of the sloped portion between the pulses is controlled via an ion compensation current; and

a calibration component receiving the modified periodic voltage function and measuring a voltage and a current of the modified periodic voltage function in the load emulator, the voltage emulating a substrate voltage associated with a plasma load and the current emulating an ion current in the plasma load.

23. The system of claim 22, wherein the calibration component reports a measured ion current based on the measured current.

24. The system of claim 22, wherein the calibration component reports a measured ion energy based on the measured voltage.

25. The system of claim 22, wherein the calibration component measures a first capacitance across an effective capacitance component of the load emulator.

26. The system of claim 25, wherein the calibration component reports a measured effective capacitance based on the measured first capacitance.

27. The system of claim 22, wherein the calibration component measures a second capacitance across a sheath capacitance component of the load emulator.

28. The system of claim 27, wherein the calibration component reports a measured sheath capacitance based on the measured second capacitance.

29. A calibration component comprising:

a load emulator configured to receive a modified periodic voltage function;

a measurement component configured to measure at least a current and a voltage within the load emulator as the modified periodic voltage function interacts with circuitry within the load emulator; and

an analysis component configured to compare the measured current and the measured voltage to an expected current and an expected voltage.

30. The calibration component of claim 29, wherein the analysis component calculates error values based on comparison of the measured current and the measured voltage to an expected current and an expected voltage, and reports the error values.

31. The calibration component of claim 30, wherein the analysis component is configured to report the error values to a bias supply that generates the modified periodic voltage function.