Tungsten chemical mechanical polishing endpoint detection

Conventional methods of controlling tungsten Chemical Mechanical Polishing (WCMP) processes have included blanket wafer polish rate and platen temperature monitoring. In order to enhance process control of WCMP, a second generation motor-current sense endpoint system was chosen as the evaluation tool. The endpoint detection system (Luxtron 9300) was installed on a WCMP polisher (IPEC 472) at the Motorola MOS6 facility. Endpoint algorithms were evaluated under various polishing conditions during time periods between pad changes. The data collected over 3 months led to a reliable endpoint recipe for both the contact and via WCMP process. The endpoint data compared with the conventional timed recipe, indicated that a time reduction at WCMP could be achieved, with a 10% increase in throughput. In addition, contact and via W-plug endpoint data showed a strong signal versus pattern density for given device types. In summary, the motor current endpoint system tested verified reliable endpoint, process control, and characterization capabilities.