Mechanisms of local planarization improvement using solo pad in chemical mechanical polishing

The mechanism of local planarization improvement using a solo pad in chemical mechanical polishing (CMP) was investigated, and the pad surface temperature was found to be the key factor. The use of a solo pad results in better planarity than that of a stacked pad under the same process conditions. When Cu CMP evaluation was conducted at various platen temperatures, a good correlation of local planarity to pad surface temperature was confirmed regardless of the pad type. Planarity improved when the pad surface temperature was lowered, and the solo pad had a lower temperature than the stacked pad at the same platen temperature. It is considered that the solo pad has a higher heat conductance than the stacked pad, so that heat generated during polishing is transferred to the platen more easily through the solo pad than through the stacked pad. The reason for the better planarity with the lower pad surface temperature was explained by the change in pad elasticity by the temperature.