Methods and systems for polishing pad control
A method for varying a removal profile of a silicon wafer during polishing using a polishing apparatus is provided. The polishing apparatus includes a polishing pad, a polishing head assembly configured to hold the silicon wafer, a temperature sensor, and a controller. The method includes receiving, at the controller, thermal data of a portion of the polishing pad from the temperature sensor and determining, by the controller, the removal profile of the silicon wafer based at least in part on the thermal data. The method further includes operating, by the controller, the polishing head assembly to position the silicon wafer in contact with the polishing pad and to selectively vary the removal profile of the silicon wafer based at least in part on the thermal data.
1. A method for varying a removal profile of a silicon wafer during polishing using a polishing apparatus comprising a polishing pad having a surface for contacting the silicon wafer, a polishing head assembly configured to hold the silicon wafer, a temperature sensor, and a controller, the method comprising:
placing the silicon wafer in the polishing apparatus;
receiving, at the controller, sets of thermal data of a portion of the polishing pad from the temperature sensor, each set of thermal data comprising temperature measurements for different points on the surface of the polishing pad, and each set of thermal data being collected from a polishing operation on a different silicon wafer;
determining an average temperature profile of the portion of the polishing pad by averaging, for each point of the different points, the temperature measurements from the sets of thermal data;
determining, by the controller, the removal profile of the silicon wafer based at least in part on the average temperature profile, wherein the removal profile comprises a cross sectional profile of the silicon wafer;
operating, by the controller, the polishing head assembly to position the silicon wafer in contact with the polishing pad and to selectively vary the removal profile of the silicon wafer based at least in part on the average temperature profile; and
polishing the silicon wafer using the polishing pad.
2. The method of claim 1 , wherein receiving the sets of thermal data of the polishing pad from a temperature sensor comprises receiving the sets of thermal data of the polishing pad from an infrared (IR) camera.
3. The method of claim 1 , wherein the polishing head assembly comprises a polishing head and a cap, wherein the cap selectively varies the removal profile of the silicon wafer.
4. The method of claim 3 , wherein the cap defines a chamber, wherein the polishing head assembly selectively varies the removal profile of the silicon wafer by regulating the pressure within the chamber.
5. The method of claim 4 , wherein the chamber is connected to a pressurizing source, the method further comprising regulating the pressure within the chamber with the pressurizing source.
6. The method of claim 5 , wherein the cap includes a floor, wherein regulating the pressure within the chamber with the pressurizing source selectively varies the removal profile of the silicon wafer by regulating the shape of the floor.
7. The method of claim 1 , wherein the temperature sensor is located adjacent to the polishing pad.
8. The method of claim 1 , wherein the temperature sensor is positioned to capture the sets of thermal data with the different points on the surface of the polishing pad being located along a radius of the polishing pad.
9. A method for varying a removal profile of a silicon wafer during polishing using a polishing apparatus comprising a polishing pad having a surface for contacting the silicon wafer, a polishing head assembly configured to hold the silicon wafer, a temperature sensor, and a controller, the method comprising:
placing the silicon wafer in the polishing apparatus;
receiving, at the controller, sets of thermal data of a portion of the polishing pad from the temperature sensor, each set of thermal data comprising temperature measurements for different points on the surface of the polishing pad, and each set of thermal data being collected from a polishing operation on a different silicon wafer;
determining an average temperature profile of the portion of the polishing pad by averaging, for each point of the different points, the temperature measurements from the sets of thermal data;
determining a differential temperature between two points of the different points in the average temperature profile;
determining, by the controller, the removal profile of the silicon wafer based on the average temperature profile, wherein the removal profile comprises a cross sectional profile of the silicon wafer;
operating, by the controller, the polishing head assembly to position the silicon wafer in contact with the polishing pad and to selectively vary the removal profile of the silicon wafer by comparing the determined differential temperature to a reference differential temperature; and
polishing the silicon wafer using the polishing pad.
10. The method of claim 9 , wherein receiving the sets of thermal data of the polishing pad from a temperature sensor comprises receiving the sets of thermal data of the polishing pad from an infrared (IR) camera.
11. The method of claim 9 , wherein the different points on the surface of the polishing pad are located along a radius of the polishing pad.
12. The method of claim 9 , wherein the polishing head assembly comprises a polishing head and a cap, and wherein the cap selectively varies the removal profile of the silicon wafer.
13. The method of claim 12 , wherein the cap defines a chamber, and wherein the polishing head assembly selectively varies the removal profile of the silicon wafer by regulating the pressure within the chamber.