Inductive monitoring of conductive trench depth

A computer program product encoded on a non-transitory computer storage medium, operable to cause a processor to perform operations to control a polishing operation, the operations comprising:

• receiving a signal from an inductive monitoring system generated by intermittently passing a magnetic field through a closed conductive loop formed of a conductive material in a trench in a layer of a substrate undergoing polishing;
• and
• extracting from the signal a sequence of values over time, the sequence of values representing depth of the conductive material over time;
• and
• at least one of
• detecting a polishing endpoint by determining from the sequence of values that a depth of the conductive material has reached a target depth, or
• causing at least one pressure applied by a carrier head to the substrate to be adjusted during polishing of a layer at a polishing station based on the sequence of values such that different zones on the substrate have closer to the same endpoint time than without such an adjustment.

An apparatus for chemical mechanical polishing, comprising:

• a platen having a surface to support a polishing pad;
• a carrier head to hold a substrate such that a layer on the substrate contacts the polishing pad;
• an inductive sensor to monitor a depth of a conductive material in a trench in the layer on the substrate by generating a magnetic field that intermittently passes through a closed conductive loop in the layer of the substrate;
• and
• a controller configured to receive a signal from the inductive sensor and extract a sequence of values over time from the signal, the sequence of values representing a depth of a conductive material in a trench in the layer providing the closed conductive loop, the controller configured to at least one of detect a polishing endpoint by determining from the sequence of values that the depth of the conductive material has reached a target depth, or adjust at least one pressure applied by the carrier head to the substrate during polishing of the layer based on the sequence of values such that different zones on the substrate have closer to the same endpoint time than without such an adjustment.