A dual controller APC engine used for CMP applications

Chemical Mechanical Polishing (CMP) is used as a common semiconductor manufacturing process to planarize the wafer topology. Typical operating methodology requires that a Look Ahead Test wafer first be processed from the product lot and purposely underpolished to prevent scrapping that wafer. Post process metrology is then done and the proper process parameters are calculated for that specific lot. Prior to starting the balance of the product lot, the original Look Ahead Test wafer is repolished if it is out of control limits. This process is repeated for the next lot. This methodology is labor intensive, prone to error and impacts the cycle time or Units per Hour (UPH) of this manufacturing process. Each of these factors contribute to degrading the efficiency of the CMP operation because more operators and tools are needed to produce the required quantity of material. Risk of a large margin of error exists when operators are allowed to manipulate recipe parameters, which can result in out of spec material that would need to be scrapped. An Advanced Process Control engine was developed that increased UPH while improving Cpk.