Sensor array for measuring plasma characteristics in plasma processing environments
View Patent ↗A plasma processing system is provided with diagnostic apparatus for making in-situ measurements of plasma properties. The diagnostic apparatus generally comprises a non-invasive sensor array disposed within a plasma processing chamber, an electrical circuit for stimulating the sensors, and means for recording and communicating sensor measurements for monitoring or control of the plasma process. In one form, the sensors are dynamically pulsed dual floating Langmuir probes that measure incident charged particle currents and electron temperatures in proximity to the plasma boundary or boundaries within the processing system. The plasma measurements may be used to monitor the condition of the processing plasma or furnished to a process system controller for use in controlling the plasma process.
1. A method of measuring plasma boundary properties in a plasma processing system, comprising:
a) providing a plasma processing system having a plasma chamber;
b) providing a sensor array comprising a plurality of electrically floating sensors disposed within the plasma chamber;
c) creating a plasma within the plasma chamber for use in a plasma process; and
d) measuring boundary properties of the plasma using the sensor array.
2. The method of claim 1 , wherein the sensors are dual floating Langmuir probes.
3. The method of claim 1 , wherein the sensor array is disposed along a chamber liner contained within the plasma chamber.
4. The method of claim 1 , wherein the sensor array is disposed along a dielectric isolation ring contained within the plasma chamber.
5. The method of claim 1 , wherein the sensor array is disposed about a workpiece chuck contained within the plasma chamber.
6. The method of claim 1 , wherein the boundary properties of the plasma are measured in real time.
7. The method of claim 1 , wherein the measured boundary properties of the plasma are used to compute bulk properties of the plasma.
8. The method of claim 1 , wherein the measured boundary properties of the plasma are furnished to a process system controller that controls the plasma process.
9. The method of claim 1 , wherein the plurality of sensors is dynamically pulsed to measure boundary properties of the plasma.
10. The method of claim 9 , wherein the plasma is created using a pulsed power source and the dynamic pulsing of the plurality of sensors is synchronized with the pulsing of the pulsed power source.
11. A plasma processing system, comprising:
a) a plasma chamber in which a processing plasma may be created;
b) a sensor array comprising a plurality of electrically floating sensors disposed within the plasma chamber; and
c) a circuit for stimulating the plurality of sensors to measure boundary properties of the processing plasma.
12. The system of claim 11 , wherein the sensors are dual floating Langmuir probes.
13. The system of claim 11 , wherein the sensor array is disposed along a chamber liner contained within the plasma chamber.
14. The system of claim 11 , wherein the sensor array is disposed along a dielectric isolation ring contained within the plasma chamber.
15. The system of claim 11 , wherein the sensor array is disposed about a workpiece chuck contained within the plasma chamber.
16. The system of claim 11 , wherein the circuit for stimulating the plurality of sensors is a dynamic pulsing circuit.
17. The system of claim 11 , wherein the circuit for stimulating the plurality of sensors is a multiplex circuit.
18. The system of claim 11 , further comprising a circuit for recording and communicating measured boundary properties of the plasma to a process system controller.