Polishing apparatus and polishing method
A film thickness measuring apparatus and an end point detector monitor a film thickness of a conductive film based on an output of an eddy current sensor disposed in a polishing table. The output of the eddy current sensor includes an impedance component, and when a resistance component and a reactance component of the impedance component are associated with the respective axes of a coordinate system having two orthogonal coordinate axes, at least some points on the coordinate system corresponding to the impedance component form at least a part of a circle. The film thickness measuring apparatus determines a distance between a point on the coordinate system and the center of the circle, determines the film thickness from the impedance component and corrects the determined film thickness using the determined distance.
1 . A polishing apparatus comprising:
a rotatable polishing table;
a top ring;
an eddy current sensor disposed in the polishing table;
a monitoring circuit;
a processor; and
a non-transitory storage medium having executable instructions stored thereon;
wherein the executable instructions, when executed by the processor, cause the apparatus to perform operations including:
holding, by the rotatable polishing table, a polishing pad having a polishing surface;
pressing, by the top ring, a substrate to be polished against the polishing surface and polishing a conductive film on the substrate;
monitoring, by the monitoring circuit, a film thickness of the conductive film based on an output of the eddy current sensor, wherein
the output of the eddy current sensor includes an impedance component,
when a resistance component and a reactance component of the impedance component are associated with respective axes of a coordinate system having two orthogonal coordinate axes, at least some points on the coordinate system corresponding to the impedance component form at least a part of a circle, and
determining, by the monitoring circuit, a first distance between the point on the coordinate system and a center of the circle, and determining a film thickness from the impedance component and correcting the determined film thickness using the determined first distance.
2 . The polishing apparatus according to claim 1 , wherein the executable instructions, when executed by the processor, further cause the apparatus to perform operations including:
performing, by the monitoring circuit, the correction using a predetermined correction coefficient in accordance with the first distance.
3 . The polishing apparatus according to claim 1 , wherein the executable instructions, when executed by the processor, further cause the apparatus to perform operations including:
performing, by the monitoring circuit, the correction on the film thickness obtained in a peripheral part of the substrate.
4 . The polishing apparatus according to claim 1 , wherein the executable instructions, when executed by the processor, further cause the apparatus to perform operations including:
determining, by the monitoring circuit, a second distance corresponding to a radius of the circle and perform the correction using the first distance and the second distance.
5 . The polishing apparatus according to claim 1 , further comprising a temperature sensor and a temperature correction unit:
wherein the executable instructions, when executed by the processor, further cause the apparatus to perform operations including:
directly or indirectly measuring, by the temperature sensor a temperature of the substrate under polishing; and
further correcting, by the temperature correction unit, the corrected film thickness using the measured temperature.