Spatial monitoring and control of plasma processing environments
Systems and methods for plasma processing are disclosed. An exemplary system may include a plasma processing chamber comprising a source to produce a plasma in the processing chamber and at least two bias electrodes arranged within the plasma processing chamber to control plasma sheaths proximate to the bias electrodes. A chuck is disposed to support a substrate, and a source generator is coupled to the plasma electrode. At least one bias supply is coupled to the at least two bias electrodes, and a controller is included to control the at least one bias supply to control the plasma sheaths proximate to the bias electrodes.
1. A method for plasma processing, the method comprising:
sustaining a plasma in a plasma processing chamber by inductively coupling a primary inductor to n secondary inductors so current that passes through each of the n secondary inductors results from mutual inductance through the plasma with the primary inductor;
applying an asymmetric periodic voltage waveform to each of a plurality of zones in the plasma processing chamber with a plurality of corresponding bias supplies;
adjusting at least one of current though one or more of the n secondary inductors or one or more characteristics of the asymmetric periodic voltage waveforms to alter a spatial distribution of the plasma.
2. The method of claim 1 , comprising:
monitoring at least one characteristic of the power that is applied by each of the corresponding bias supplies, and wherein the adjusting is based upon the monitoring.
3. A method for plasma processing, the method comprising:
sustaining a plasma in a plasma processing chamber by inductively coupling a primary inductor to n secondary inductors so current that passes through each of the n secondary inductors results from mutual inductance through the plasma with the primary inductor;
applying an asymmetric periodic voltage waveform to the plasma processing chamber with a bias supply;
adjusting at least one of current though one or more of the n secondary inductors or one or more characteristics of the asymmetric periodic voltage waveforms to alter a spatial distribution of the plasma; and
calculating ion current in a zone of the plasma processing chamber based upon at least one characteristic of the power that is applied by the bias supply;
wherein the adjusting is based upon the calculated ion current in the zone.
4. The method of claim 3 , comprising:
applying an asymmetric periodic voltage waveform to each of a plurality of zones in the plasma processing chamber with a corresponding bias supply; and
calculating ion current in each of the plurality of zones in the plasma processing chamber based upon at least one characteristic of the power that is applied by each of the plurality of bias supplies.
5. The method of claim 4 , wherein the adjusting comprises adjusting density of the plasma proximate to each of the plurality of zones by adjusting current though one or more of the n secondary inductors based upon at least one characteristic of the power that is applied by each of the plurality of bias supplies.
6. The method of claim 4 , wherein the adjusting comprises adjusting density of the plasma proximate to each of the plurality of zones by adjusting one or more characteristics of the asymmetric periodic voltage waveforms.
7. A non-transitory computer-readable medium comprising instructions stored thereon, for at least one of execution by a processor or for configuring a field programmable gate array, to perform plasma processing, the instructions comprising instructions to:
maintain a plasma in a plasma processing chamber by controlling current in n secondary inductors, wherein n is greater than or equal to one and the current in the n secondary inductors results from mutual inductance through the plasma with a primary inductor;
apply an asymmetric periodic voltage waveform to the plasma processing chamber with a bias supply;
monitor at least one characteristic of the power that is applied by the bias supply; and
adjust, based upon the monitoring, at least one of:
current though one or more of the n secondary inductors or one or more characteristics of the asymmetric periodic voltage waveform to alter a spatial distribution of the plasma.
8. The non-transitory computer-readable medium of claim 7 , comprising instructions to:
calculate ion current in a zone of the plasma processing chamber based upon at least one characteristic of the power that is applied by the bias supply; and
wherein the instructions to adjust include instructions to adjust based upon the calculated ion current in the zone.
9. The non-transitory computer-readable medium of claim 7 , comprising instructions to:
apply an asymmetric periodic voltage waveform to each of a plurality of zones in the plasma processing chamber with a corresponding bias supply; and
calculate ion current in each of the plurality of zones in the plasma processing chamber based upon at least one characteristic of the power that is applied by each of the plurality of bias supplies.
10. The non-transitory computer-readable medium of claim 9 , wherein the instructions to adjust comprise instructions to adjust a density of the plasma proximate to each of the plurality of zones by adjusting current though one or more of the n secondary inductors based upon the calculated ion current in one or more of the plurality of zones.
11. The non-transitory computer-readable medium of claim 9 , wherein the instructions to adjust comprise instructions to adjust a density of the plasma proximate to each of the plurality of zones by adjusting one or more characteristics of the asymmetric periodic voltage waveforms based upon the calculated ion current in one or more of the plurality of zones.
12. A system for controlling a plasma in a processing chamber, the system comprising:
a source generator;
a primary inductor coupled to the source generator to excite the plasma when power is actively applied by the source generator to the primary inductor;
n secondary inductors positioned relative to the primary inductor so that current that passes through the n secondary inductors results from mutual inductance through the plasma with the primary inductor, wherein n is greater than or equal to one;
a terminating element coupled to each of the n secondary inductors to form n terminating elements, the terminating element affecting the current through a corresponding secondary inductor to affect the spatial distribution of the plasma;
at least one electrical plane arranged within the plasma processing chamber to control a plasma sheath proximate to the at least one electrical plane;
at least one bias supply coupled to the at least one electrical plane; and
at least one controller coupled to the at least one bias supply to apply an asymmetric periodic voltage waveform to the at least one electrical plane to control the plasma sheath proximate to the electrical plane,
wherein the terminating element is an impedance-adjustable terminating element to enable current through the at least one secondary inductor to be controlled by the at least one controller based upon an indication of a level of ion current in the plasma proximate to the at least one electrical plane.
13. The system of claim 12 wherein the indication of the level of ion current is obtained from at least one characteristic of power that is applied by the at least one bias supply to the at least one electrical plane.
14. The system of claim 12 , comprising at least one sensor coupled to at least one of the n terminating elements, wherein the controller is adapted to regulate the current through the at least one of the n terminating elements responsive to a signal from the at least one sensor to regulate the plasma density.
15. The system of claim 14 , wherein the at least one sensor includes a current sensor and wherein the impedance-adjustable terminating elements include a variable capacitor.