Method and apparatus of arrayed sensors for metrological control
View Patent ↗A system for processing a wafer is provided. The system includes a chemical mechanical planarization (CMP) tool. The CMP tool includes a wafer carrier defined within a housing. A carrier film is affixed to the bottom surface and supports a wafer. A sensor embedded in the wafer carrier. The sensor is configured to induce an eddy current in the wafer to determine a proximity and a thickness of the wafer. A sensor array external to the CMP tool is included. The sensor array is in communication with the sensor embedded in the wafer carrier and substantially eliminates a distance sensitivity. The sensor array provides an initial thickness of the wafer to allow for a calibration to be performed on the sensor embedded in the wafer carrier. The calibration offsets variables causing inaccuracies in the determination of the thickness of the wafer during CMP operation. A method and an apparatus are also provided.
1. A method for determining an endpoint thickness for a chemical mechanical planarization (CMP) operation, comprising:
providing a first sensor including two coupled eddy current sensors external to the CMP module, wherein the two coupled eddy current sensors include a top sensor and a bottom sensor, an axis of the top sensor being offset from an axis of the bottom sensor;
detecting a thickness of a wafer with the first sensor;
supplying the thickness of the wafer to a second sensor in the CMP module;
calibrating the second sensor with the thickness of the wafer; and
adjusting CMP operating parameters based on a signal from the second sensor in order to optimize a CMP operation for the wafer.
2. The method of claim 1 , wherein the first sensor is an array of eddy current sensors, the array of eddy current sensors configured so that a thickness of the wafer is calculated between a top point on the top surface of the wafer and a bottom point on a bottom surface of the wafer, the top point and the bottom point sharing a common vertical axis through the wafer.
3. The method of claim 1 , wherein the coupled eddy current sensors includes a top sensor and a bottom sensor, the top sensor and the bottom sensor sharing a vertical axis, a signal from the top sensor being out of phase with a signal from the bottom sensor in order to substantially eliminate signal suppression.
4. A method for monitoring a chemical mechanical planarization (CMP) operation, comprising method operations of:
determining an incoming thickness of a wafer prior to the CMP operation with a first sensor;
communicating the thickness to a sensor embedded in a wafer carrier of a CMP module: and
calibrating the embedded sensor with the thickness to substantially eliminate variability in an in-process thickness measurement due to carrier film non-uniformity and pad erosion, wherein the first sensor and the embedded sensor are eddy current sensors.
5. The method of claim 4 , wherein the first sensor includes two coupled eddy current sensors.
6. The method of claim 5 , further comprising:
offsetting an axis associated with one of the two coupled eddy current sensors with an axis of an other of the two coupled eddy current sensors.
7. A method for monitoring a chemical mechanical planarization (CMP) operation, comprising method operations of:
determining an incoming thickness of a wafer prior to the CMP operation with a first sensor;
communicating the thickness to a sensor embedded in a wafer carrier of a CMP module;
calibrating the embedded sensor with the thickness to substantially eliminate variability in an in-process thickness measurement due to carrier film non-uniformity and pad erosion;
detecting an endpoint thickness of the wafer with the embedded sensor; and
terminating the operation.
8. The method of claim 7 , wherein the first sensor and the embedded sensor are eddy current sensors.
9. The method of claim 7 , wherein the first sensor includes two coupled eddy current sensors.
10. The method of claim 9 , further comprising:
offsetting an axis associated with one of the two coupled eddy current sensors with an axis of an other of the two coupled eddy current sensors.