Chemical mechanical polishing endpoint detection

An in-situ endpoint detection system to polish a multilayer semiconductor substrate comprising:

• a chemical mechanical polisher coupled to the multilayer semiconductor substrate configured to remove a first layer;
• a polishing solution dispenser configured to apply polishing solution to the multilayer semiconductor substrate during removal of the first layer;
• and
• an endpoint detector coupled to the chemical mechanical polisher configured to pump used polishing solution through a receiving conduit to determine whether a concentration of the first layer in the used polishing solution is within a predetermined range.

A chemical mechanical polishing system to polish a multilayer workpiece comprising:

• a chemical mechanical polisher coupled to the multilayer workpiece configured to remove a first layer from the multilayer workpiece;
• a carrier head controller coupled to the chemical mechanical polisher configured to control the chemical mechanical polisher;
• a polishing solution dispenser configured to apply polishing solution to the multilayer workpiece and the chemical mechanical polisher during removal of the first layer;
• a polishing solution conduit configured to receive used polishing solution;
• an optical detector coupled to the polishing solution conduit configured to direct an optical beam through the polishing solution conduit to measure an absorption characteristic of the used polishing solution;
• and
• a processor coupled to the optical detector and the carrier head controller configured to send a halt signal to the carrier head controller in response to an absorption characteristic outside a predetermined range.