Advanced Cu CMP pad for reducing scratches

The requirements for reducing scratching during the Chemical Mechanical Planarization (CMP) process have been getting tighter and more stringent in order to improve semiconductor chip yield. In this paper, we analyze platen torque data generated from the torque monitoring system built into a CMP polisher to demonstrate that the addition of a hydrophilic polymer to the CMP pad matrix resulted in reduced friction during CMP. We attribute the observation of the reduced torque to the Toms effect discovered in rheology in 1948. The hydrophilic polymers not only reduce friction but also have great impact on reducing scratch formation on wafers. PEO-1 (Polyethylene oxide MW=150K-400K) performed best, in terms of scratch reduction, among the polymers tested. This new hydrophilic pad enables advanced CMP performance, in particular low defectivity, without a negative impact on removal rate.