An apparatus and method for stopping mechanical and chemical-mechanical
polishing of a substrate at a desired endpoint. In one embodiment, a
polishing machine has a platen, a polishing pad positioned on the platen,
and a polishing medium located at a planarizing surface of the polishing
pad. The polishing machine also has a substrate carrier that may be
positioned over the planarizing surface of the polishing pad, and at
least one heat sensor is coupled to the polishing machine to detect heat
at a front side of the substrate. The heat sensor preferably measures a
temperature of a component sensitive to heat at the front side of the
substrate, such as the planarizing surface of the polishing pad, the back
side of the substrate, or the byproducts produced by polishing the
substrate. In operation, the heat sensor monitors the heat at the front
side of the substrate, and the removal of material from the substrate is
stopped when the heat at the front side of the substrate changes from a
first heat range to a second heat range.