Systems and methods for monitoring faults, anomalies, and other characteristics of a switched mode ion energy distribution system

1. A system for monitoring a plasma processing chamber, the system comprising:

a power supply configured to provide a periodic voltage function to an output that is configured to couple to the plasma processing chamber, the periodic voltage function having pulses and a portion between the pulses;

an ion current compensation component configured to provide ion current compensation, I c , to the output to modify a slope, dV 0 /dt, of the portion between the pulses to form a modified periodic voltage function;

a memory to store an effective capacitance value, C 1 , of at least a substrate support of the plasma processing chamber; and

a controller in communication with the power supply, the ion current compensation component, a non-transitory tangible computer readable medium, and the memory, wherein the non-transitory tangible computer readable medium is encoded with instructions, and wherein the controller is configured to execute the instructions, the instructions comprising:

determining the slope, dV 0 /dt, of the portion between the pulses of the modified periodic voltage function;

adjusting a magnitude of the ion current compensation, I C , until

ⅆ

V

0

ⅆ

t

-

I

C

C

1

=

0

;

and

monitoring changes of compensation current, I C , over time to monitor a condition of the processing chamber.

2. A system for monitoring a plasma processing chamber, the system comprising:

a power supply configured to provide a periodic voltage function to an output that is configured to couple to the plasma processing chamber, the periodic voltage function having pulses and a portion between the pulses;

an ion current compensation component configured to provide ion current compensation, I C , to the output to modify a slope of the portion between the pulses to form a modified periodic voltage function, the ion current compensation component including:

a controllable DC current source, controlling for current, that is consistently coupled to the output; and

a current controller encoded to maintain a constant rate of change of a voltage of the portion between the pulses by:

determining a slope, dV 0 /dt, of the portion between the pulses of the modified periodic voltage function;

controlling the controllable DC current source to adjust a magnitude of the ion current compensation, I C , until

ⅆ

V

0

ⅆ

t

-

I

C

C

1

=

0

;

and

a controller configured to monitor changes of I c over time to monitor a condition of the processing chamber.

3. A system for monitoring a plasma processing chamber, the system comprising:

a DC power supply that provides a DC voltage that is fixed at a magnitude responsive to an ion-energy setting, wherein the ion-energy setting is indicative of a monoenergetic distribution of ion energy at the surface of a substrate within the plasma processing chamber;

an output disposed to couple to a substrate support;

two switching components including a first switching component coupled to the DC power supply and a second switching component couple to a ground terminal, the two switching components configured to generate a periodic voltage function at the output by alternately coupling the DC voltage and the ground terminal to the output, the periodic voltage function having pulses and a portion between the pulses; and

an ion current compensation component coupled to the output, the ion current compensation component including:

a controllable DC current source, separate from the DC power supply, that is consistently coupled to the output; and

a current controller configured to monitor a rate of change of a voltage of the portion between the pulses and maintain an uninterrupted ion current compensation current, I C , which is fixed in magnitude, to maintain a fixed rate of change of the voltage; and

a controller configured to monitor changes of I c over time to monitor a condition of the processing chamber.

4. The system of claim 1 , wherein the effective capacitance value, C 1 , includes capacitances of an electrical path between the output and the substrate support as well as one or more capacitances of the substrate support.

5. The system of claim 4 , wherein the effective capacitance value, C 1 , also accounts for a capacitance of the substrate.

6. The system of claim 5 , wherein the effective capacitance value, C 1 , also accounts for insulation coupled to the substrate support.

7. The system of claim 1 , wherein the power supply is configured to be DC-coupled to the plasma processing chamber.

8. The system of claim 1 , wherein the controller instructions further include comparing the modified periodic voltage function to a reference waveform, wherein differences between the modified periodic voltage function and the reference waveform are indicative of a fault.

9. The system of claim 1 , wherein the controller instructions further include comparing portions of each cycle of the modified periodic voltage function to each other, and if variations between cycles above a threshold are observed, then a fault indication is triggered.

10. The system of claim 1 , wherein the controller instructions further include identifying a fourth portion of the modified periodic voltage function, and if this fourth portion has a nonlinear slope, then identifying a nonlinear change in capacitance of the system.

11. The system of claim 2 , wherein the controllable DC current source comprises at least a power supply in series with an inductive element.

12. The system of claim 2 , wherein the controller instructions further include:

altering an amplitude of voltage of the modified periodic voltage function generated by the power supply; and

adjusting the DC current source such that the modified periodic voltage function is altered to a greater extent than if one of the voltage or ion current compensation were altered alone.

13. The system of claim 2 , wherein the controller instructions further include comparing the modified periodic voltage function to a reference waveform, wherein differences between the modified periodic voltage function and the reference waveform are indicative of a fault in the system.

14. The system of claim 2 , wherein the controller instructions further include comparing portions of each cycle of the modified periodic voltage function to each other, and if variations between cycles above a threshold are observed, then a fault indication is triggered.

15. The system of claim 2 , wherein the controller instructions further include identifying a portion of the modified periodic voltage function having a slope dV 0 /dt, and if this slope is nonlinear, then recognizing that the system is experiencing a nonlinear change in capacitance.

16. The system of claim 3 , wherein the controller instructions further include comparing the modified periodic voltage function to a reference waveform, wherein differences between the modified periodic voltage function and the reference waveform are indicative of a fault in the system.

17. The system of claim 3 , wherein the controller instructions further include comparing portions of each cycle of the modified periodic voltage function to each other, and if variations between cycles above a threshold are observed, then a fault indication is triggered.

18. The system of claim 3 , wherein the controller instructions further include determining slope dV 0 /dt, and if this slope is nonlinear, then recognizing that the system is experiencing a nonlinear change in capacitance.

19. The system of claim 1 , wherein the tangible computer readable medium and the memory are the same.