CMP pad surface uniformity optimization after polish

Aiming at CMP (Chemical Mechanical Polisher) pad thickness uniformity optimization and pad lifetime extension, we performed optimal design to do experiments finding the optimal process condition. We obtained much longer using time of pad and better pad uniformity on CMP tool from wafer stay time distribution on pad by zone. Base on the results of DOE (Design of Experiment), we get the best setting of stay time ratio by zone for optimal pad thickness uniformity is 18%/ 20% (zone1/ zone10). Also we estimated a mechanism of pad thickness uniformity maintenance after polish in CMP process.