Investigation of the pad-conditioning performance deterioration in the chemical mechanical polishing process

The surface roughness of a chemical mechanical polishing (CMP) pad provides microscopic asperities where the actual polishing takes place. Thus, the roughness should be maintained in a proper regimen to obtain stable CMP process quality. A conditioner is a key consumable in the CMP process because it maintains the roughness of the CMP pad surface against surface glazing or flattening during polishing. Because the conditioner mechanically breaks the pad surface to maintain the roughness, previous research has expressed its ability index in terms of the pad wear rate (PWR). In the present study, we investigate the reason for PWR change of CMP pads having vigorously changing moduli with respect to temperature changes during the mass production. The pad property changed steeply in the process temperature range from 60 to 80 °C. The tensile strength is a key property change that leads to sudden PWR drop. We found that the shape and configuration of the diamond tip are the major parameters affecting the ability to maintain surface roughness of the pads. Thus, we suggested a proper conditioner design for tungsten (W) CMP based on the experimental data to sustain the process quality and increase the consumable lifetime. As a result, the peak surface roughness has improved from 29.4 μm to 32.6 µm and the consumable lifetime was also increased.