# Contact-Area-Changeable CMP Conditioning for Enhancing Pad Lifetime
## 3 Result and Discussion
### Comparison of Pad Lifetimes
In Case I, after 16 h of conditioning, the grooves on the pad wore out in the wafer-pad contact area, and the wafer broke during the CMP experiment. Meanwhile, conditioning experiments for Case II were conducted for up to 20 h.  
Figures 15 and 16 show the MRR and WIWNU for Cases I and II, respectively, based on the conditioning time. For Case I, the MRR decreased by approximately 44.9% from 401.3 to 221.0 nm/min during 16 h of conditioning. As shown in Figure 15, in Case I, the decrease in the MRR occurred rapidly after 12 h of conditioning. Meanwhile, in Case II, the MRR was reduced by approximately 7.4% from 387.7 to 359.0 nm/min during 20 h of conditioning. Figure 16 shows the WIWNU as a function of conditioning time. Similar to the MRR in Case I, the WIWNU remained within 3% during 12 h of conditioning and increased rapidly thereafter. In Case II, the WIWNU remained within 3% for up to 20 h, and the polishing pad was available for a longer duration compared with Case I. According to [PERSON] et al. [34], locally excessive pad wear causes a non-uniform stress distribution on the wafer during CMP. The rapid decrease in the MRR and the increase in the WIWNU after 12 h of conditioning in Case I may be due to the non-uniform stress distribution caused by locally excessive pad wear. In Case II, the pad profile in the wafer-pad contact area was relatively flat even after 20 h of conditioning, which would result in less change in the MRR and WIWNU. Figure 17a-c show the scanning electron microscope (SEM) images of the cross-sections of the polishing pads in the wafer-pad contact area. Figure 17a-c show the cross-sectional views of the as-received polishing pad, polishing pad after the experiment for Case I, and polishing pad after the experiment for Case II, respectively. For Case II, the pad grooves remained after 20 h of conditioning, whereas for Case I, which had been conditioned for 16 h, all of the grooves on the pads disappeared after the experiment. Figure 14: Material removal rate distribution as a function of conditioning time: (**a**) Case I and (**b**) Case II. While previous studies on polishing pad profiles after pad conditioning have been focused on conditioner characteristics and swing motion of the conditioning arm, this study suggests improvement of polishing pad profiles by changing the contact area between the conditioner and polishing pad. Although this study differs from the existing literature, the proposed method is not applicable to the case of the conditioning arm. Figure 9:0 Within-wafer non-uniformities of Case I and II as a function of conditioning time. Figure 9:1 Scanning electron microscope (SEM) images of the cross-sections of polishing pads in the wafer–pad contact area: (**a**) as-received, (**b**) after conditioning for Case I, and (**c**) after conditioning for Case II. Figure 9:2 Average material removal rates of Case I and II as a function of conditioning time. studies in that it demonstrates that using the contact-area-changeable CMP conditioning system can increase the life of polishing pads, it seems that additional research on contact area changes of diamond conditioners and experiments under more diverse conditioning process conditions will be needed. Further, a study on the cleaning of the conditioner to remove slurry in the space between the boundaries of the divided conditioner will likely be required.