Endpoint detection method for CMP of copper

A novel method to detect the endpoint during Cu-CMP has been developed. It is based on the determination of the Cu concentration within the slurry on the pad that has just polished the wafer. The measurement of the ion concentration is performed using a capillary and an ion-selective electrode. The endpoint of the CMP process is detected by the decrease of Cu ion concentration, which is displayed by an decreased potential at the electrode. An experimental set-up has been established which can be applied to a commercial polishing tool. The method has been tested under various process conditions. The new endpoint detection system revealed to work independently of the polishing tool and the wafer size.