Endpoint detection system for wafer polishing
View Patent ↗An wafer polishing pad assembly for use in CMP includes an optical sensor for sensing reflectivity of the wafer during polishing, and produces a corresponding signal, and transmits the signal from the rotating pad to a stationary portion of the assembly. The signal is transmitting off the pad through non-contact couplings such inductive coupling or optical couplings after being converted into signal formats enabling non-contact transmission.
1. A method of polishing a wafer, said method comprising the steps of:
providing a polishing pad for use in performing a polishing operation on a surface of the wafer and providing optical means within said polishing pad for sensing an optical characteristic of the surface during the polishing operation;
providing conductor means within the polishing pad for conducting an electrical signal from said optical means to a central portion of said polishing pad,
providing a wafer;
polishing the wafer with the polishing pad; and
sensing an optical characteristic of the surface during the polishing operation.
2. The method of claim 1 wherein the step of providing a polishing pad further comprises providing a means for transferring the electrical signal from the central portion of the polishing pad to a location remote from the polishing pad.
3. A method of polishing a wafer, said method comprising the steps of:
providing a polishing pad for use in performing a polishing operation on a surface of the wafer and providing optical means within said polishing pad for sensing an optical characteristic of the surface during the polishing operation;
providing a wafer;
polishing the wafer with the polishing pad;
sensing an optical characteristic of the surface during the polishing operation;
wherein the step of polishing the wafer comprises rotation of the pad while the pad is in contact with the wafer; and
the step of providing a polishing pad further comprises providing an inductive coupling system operable to inductively transfer an electrical signal from the pad during rotation to a stationary receiver, said inductive coupling system comprising a first transformer winding secured to the pad such that the first transformer winding rotates with the pad, and a second transformer winding within the stationary receiver, and a means to communicate the electrical signal from the optical sensor to the first transformer winding.
4. The method of claim 3 comprising the further step of transferring the electrical signal from the optical sensor to the first transformer winding.
5. The method of claim 4 comprising the further step of transferring the electrical signal from the first transformer winding to a second transformer winding.
6. The method of claim 5 comprising the further step of transferring the electrical signal from the second transformer winding to a signal processing circuit.