Asymmetry correction via oriented wafer loading
A chemical mechanical polishing system includes a metrology station having a sensor configured to measure a thickness profile of a substrate, a robotic arm configured to transfer the substrate from the metrology station to a polishing station having, a platen to support a polishing pad having a polishing surface, a carrier head on the polishing surface, the carrier head having a membrane configured to apply pressure to the substrate in the carrier head, and a controller configured to receive measurements from the sensor and configured to control the robotic arm to orient the substrate in the carrier head according to substrate profile and a removal profile for the carrier head.
1. A chemical mechanical polishing system, comprising:
a polishing station having a platen to support a polishing pad, a carrier head to hold a substrate, and a motor to rotate the carrier head;
a robotic arm configured to transfer the substrate to the polishing station; and
a controller including a processor and non-transitory computer readable medium storing a computer program having instructions to cause the controller to store an angular removal profile for the carrier head and to receive an angular thickness profile of the substrate, to select a loading orientation for the carrier head relative to the substrate based on the angular removal profile and the angular thickness profile, the selection including calculation of an angular asymmetry for a plurality of possible loading orientations and determination of one of the plurality of possible loading orientations having reduced angular asymmetry in final thickness profile relative to other possible loading orientations, to cause the motor to rotate the carrier head such that the carrier head is at the selected loading orientation, and to load the substrate into the carrier head with the carrier head at the selected loading orientation.
2. The system of claim 1 , wherein the controller is configured to, for each angular difference of a plurality of angular differences, calculate a total thickness difference between the angular removal profile and the angular thickness profile using the angular difference as angular offset between the angular removal profile and the angular thickness profile.
3. The system of claim 2 , wherein the controller is configured to select an angular difference from the plurality of angular differences that has a minimum total thickness difference.
4. The system of claim 3 , wherein the controller is configured to determine the loading orientation based on the selected angular difference.
5. The system of claim 2 , wherein the controller is configured to calculate the total thickness difference as a sum of least squared differences between the angular removal profile and the angular thickness profile.
6. The system of claim 1 , comprising a metrology station having a sensor configured to measure the angular thickness profile of the substrate.
7. The system of claim 6 , wherein the sensor comprises a line scan camera.
8. The system of claim 1 , comprising a sensor to determine an angular orientation of the substrate prior to loading of the substrate into the carrier head.
9. The system of claim 8 , wherein the sensor is configured to detect a marker on the substrate.
10. The system of claim 9 , wherein the sensor is configured to detect a flat or a notch on the substrate.
11. The system of claim 9 , wherein the controller is configured to assign a marker indicative of the angular orientation of the substrate.
12. The system of claim 8 , comprising a metrology station to measure the angular thickness profile of the substrate, and wherein the sensor is positioned in the metrology station to determine an angular orientation of the substrate in the metrology station.
13. The system of claim 1 , wherein the carrier head has one or more markers that are indicative of an angular orientation of the carrier head, and the system comprises an optical sensor to detect the marker to measure the angular orientation of the carrier head.
14. The system of claim 1 , further comprising motor encoder to measure an angular position of the carrier head.