Friction based endpoint technique for barrier polish during copper CMP

A novel method has been introduced to provide a clear endpoint signal for copper CMP barrier polish with minimal time delay as compared to conventional endpoint. A modified power sensor is installed on a 300mm polisher to measure the torque generated by the platen motor with an improved signal to noise ratio. An Extended Kalman filter (EKF) is integrated to the software to extract the friction signals while discarding the sinusoidal components due to carrier head and platen movement, and reveal clear friction endpoint. The intensity of signal is improved by changes in process and/or slurry parameters. The technique is validated by using blanket barrier films as well as patterned wafers.