Method and apparatus of eddy current monitoring for chemical mechanical polishing
A polishing system can have a rotatable platen, a polishing pad secured to the platen, a carrier head to hold a substrate against the polishing pad, and an eddy current monitoring system including a coil or ferromagnetic body that extends at least partially through the polishing pad. A polishing pad can have a polishing layer and a coil or ferromagnetic body secured to the polishing layer. Recesses can be formed in a transparent window in the polishing pad.
1. A polishing pad, comprising:
a polishing layer;
a transparent window in the polishing layer, wherein the window has a recess formed in a bottom surface thereof; and
a ferromagnetic body having an upper portion in the recess of the window and secured to the window with an adhesive and a lower portion below the bottom surface of the window, wherein a coil is wound around the ferromagnetic body.
2. The polishing pad of claim 1 , wherein the window includes a plurality of recesses formed in a bottom surface thereof, and a plurality of ferromagnetic bodies are positioned into the recesses.
3. The polishing pad of claim 1 , wherein the polishing pad further comprises a backing layer.
4. The polishing pad of claim 1 , wherein a position of the ferromagnetic body relative to a surface of the polishing layer is adjustable.
5. The polishing pad of claim 1 , wherein the ferromagnetic body is positioned with a longitudinal axis perpendicular to a surface of the polishing layer.
6. The polishing pad of claim 1 , wherein the ferromagnetic body is positioned with a longitudinal axis at an angle greater than 0 and less than 90 degrees to a surface of the polishing layer.
7. The polishing pad of claim 1 , wherein the ferromagnetic body is secured to the window with an epoxy.
8. The polishing pad of claim 1 , wherein the window is a polymer.
9. The polishing pad of claim 8 , wherein the transparent window has a top surface that is flush with a polishing surface of the polishing layer.
10. The polishing pad of claim 1 , wherein the coil is positioned below the window.
11. The polishing pad of claim 1 , wherein the ferromagnetic body projects below a bottom surface of the window.
12. The polishing pad of claim 1 , wherein the ferromagnetic body is completely enclosed in the window.
13. The polishing pad of claim 1 , wherein the body is a rod and the coil wraps around the body but is unattached to the body.
14. The polishing pad of claim 13 , wherein the coil includes electrical connections configured to be coupled to contact pads.
15. The polishing pad of claim 1 , wherein the body is a rod and the coil wraps around the body and is attached to the body.
16. The polishing pad of claim 1 , wherein the body is a rod and the coil wraps around the body outside of the recess and epoxy surrounds the body in the recess.
17. The polishing pad of claim 16 , wherein the rod is a cylinder.
18. The polishing pad of claim 16 , wherein the rod is a trapezoid.