Method and apparatus for measuring process kit centering

1. A sensor wafer, comprising:

a substrate, wherein the substrate comprises a first surface, a second surface opposite the first surface, and an edge surface between the first surface and the second surface;

a plurality of sensor regions formed along the edge surface, wherein each sensor region comprises a self-referencing capacitive sensor; and

a recess into the first surface of the substrate, wherein the recess extends to the edge surface.

2. The sensor wafer of claim 1 , wherein the plurality of sensor regions comprises at least three sensor regions.

3. The sensor wafer of claim 1 , wherein the self-referencing capacitive sensor comprises a first probe and a second probe, wherein an output phase of the first probe is 180 degrees offset from an output phase of the second probe.

4. The sensor wafer of claim 1 , wherein the recess extends back from the sensor region at least 1.0 mm.

5. The sensor wafer of claim 1 , further comprising:

a plurality of second sensor regions on the second surface of the substrate.

6. The sensor wafer of claim 5 , wherein the second sensor regions are recessed from the second surface.

7. The sensor wafer of claim 1 , further comprising an electric field guard below each of the plurality of sensor regions.

8. The sensor wafer of claim 1 , further comprising:

a computing module, wherein the computing module is communicatively coupled to the plurality of sensor regions.

9. The sensor wafer of claim 8 , wherein the computing module comprises one or more of a power source, a processor, a memory, and a wireless communications module.

10. The sensor wafer of claim 1 , wherein the substrate has a diameter that is 300 mm.

11. A method of determining the position of a process kit in a chamber, comprising:

placing a process kit into a chamber around a support surface;

placing a sensor wafer onto the support surface, wherein the sensor wafer comprises a first surface that is supported by the support surface, a second surface opposite the first surface, and an edge surface connecting the first surface to the second surface, and wherein a plurality of sensor regions are formed on the edge surface;

determining a gap distance between each of the plurality of sensor regions and a surface of the process kit;

determining a center-point offset of a center-point of the process kit relative to a center-point of the sensor wafer from the gap distances; and

adjusting a position of the process kit when the center-point offset exceeds a predesignated threshold.

12. The method of claim 11 , wherein the plurality of sensor regions comprise self-referencing capacitive sensors.

13. The method of claim 12 , wherein the self-referencing capacitive sensors comprise a first probe and a second probe, wherein an output phase of the first probe is 180 degrees offset from an output phase of the second probe.

14. The method of claim 11 , further comprising:

determining a second center-point offset, wherein the second center-point offset is the offset of the center-point of the sensor wafer relative to a center-point of the support surface.

15. The method of claim 14 , wherein second sensor regions on the first surface of the sensor wafer are used to determine the second center-point offset.

16. The method of claim 15 , further comprising:

determining a total offset, wherein the total offset is determined by adding the first center-point offset to the second center-point offset.

17. A method of determining the position of a process kit in a chamber, comprising:

placing a process kit into a chamber around a support surface;

placing a sensor wafer onto the support surface, wherein the sensor wafer comprises a first surface that is supported by the support surface, a second surface opposite the first surface, and an edge surface connecting the first surface to the second surface, and wherein a first plurality of sensor regions are formed on the edge surface and a second plurality of sensor regions are formed on the first surface;

determining a gap distance between each of the plurality of first sensor regions and a surface of the process kit;

determining a first center-point offset from the gap distances, wherein the first center-point offset is an offset of a center-point of the process kit relative to a center-point of the sensor wafer;

determining a plurality of edge locations of the support surface with the plurality of second sensor regions;

determining a second center-point offset with the plurality of edge locations, wherein the second center-point offset is an offset of a center-point of the support surface relative to the center-point of the sensor wafer;

determining a total offset, wherein the total offset is determined by adding the first center-point offset to the second center-point offset; and

adjusting the position of the process kit when the total offset exceeds a predesignated threshold.

18. The method of claim 17 , wherein the first plurality of sensor regions comprise self-referencing capacitive sensors.