US Patent 7008296 Data processing for monitoring chemical mechanical polishing

Methods and apparatus to implement techniques for monitoring polishing a substrate. Two or more data points are acquired, where each data point has a value affected by features inside a sensing region of a sensor and corresponds to a relative position of the substrate and the sensor as the sensing region traverses through the substrate. A set of reference points is used to modify the acquired data points. The modification compensates for distortions in the acquired data points caused by the sensing region traversing through the substrate. Based on the modified data points, a local property of the substrate is evaluated to monitor polishing.