# Contact-Area-Changeable CMP Conditioning for Enhancing Pad Lifetime
## 3 Result and Discussion
### Comparison of Pad Lifetimes  
Prior to the marathon experiment on CMP conditioning, we conducted experiments on the pad cut rate profiles of Cases I and II. The conditioning experiment was conducted using the same method as the simulation conditions, and, after the experiment, the thickness profile of the polishing pad was measured using the PMS. In this study, the results  
Figure 8: Average pad cut rate of conditioning cases: (**a**) total area and (**b**) wafer–pad contact area. Figure 9: Maximum pad cut rate of conditioning cases: (**a**) total area and (**b**) wafer–pad contact area. were normalized using each average value to compare the experimental and simulation results. In the experiment, the pad cut rate profile was obtained from the difference in pad thickness profiles before and after conditioning. Figures 10 and 11 show the normalized simulated and experimental pad cut rate profiles of Cases I and II, respectively. Experiments confirmed that the simulated pad cut rate profile exhibited a shape similar to that of the pad cut rate profile measured in the experiment. In the range of 0 to 25 mm, the variation in measured signal is not large because grooves do not exist on the surface of the polishing pad. The jagged pad profile in the range of 25 mm or more is due to grooves on the polishing pad surface. The difference between the simulation and experimental results at both ends of the profile appeared to be due to the time delay during the right and left turns of the swing-arm. Furthermore, as [PERSON] [34] claimed, the difference between simulation and experimental results appears to be due to the moment caused by friction between the conditioner and the pad due to the gimbaled joint of the conditioner. In the marathon experiment on CMP conditioning, the pad profile was measured using the PMS after conditioning, and the slurry was supplied continuously during conditioning. The conditioning conditions are shown in Table 1 of Section 2.1. To determine the lifetime of the abrasive pad, CMP tests were conducted using 200-mm-diameter SiO\({}_{2}\) wafers, and  
Figure 11: Normalized pad cut rate profile of Case II: (**a**) simulation result and (**b**) experimental result. Figure 10: Normalized pad cut rate profile of Case I: (**a**) simulation result and (**b**) experimental result. the MRR and WIWNU were measured. The equations for the MRR and WIWNU are as shown in Equations (2) and (3), respectively. \[\text{MRR}(\text{nm}/\text{min})=\frac{Initial\;film\;thickness-Final\;film\;thickness}{Polishing\;time} \tag{2}\]  
\[\text{WIWNU}(\%)=\frac{\sigma}{MRR_{avg}}\times 100 \tag{3}\]  
where \(\sigma\) and \(MRR_{avg}\) represent the standard deviation of the MRR and average MRR, respectively. Figure 12 shows the pad thickness and profile change after conditioning for Case I. The average pad cut rate in Case I was 43.4 \(\upmu\)m/h based on the experimental result. Similar to the simulation results, the maximum pad wear in the pad profile occurred at a position 250 to 300 mm from the pad's center. In particular, pad wear was significant in areas where the wafer and polishing pad were in contact with each other. As shown in Figure 13, Case II had a lower pad cut rate (22.2 \(\upmu\)m/h) than Case I and exhibited a flat pad profile in the wafer-pad contact area. As shown in Figures 12 and 13, the pad profile was generally tilted, but the CMP polishing head exhibited a gimbal structure that enabled it to resemble the tilted surface of the pad when it established contact with the wafer. Figure 12: Pad thickness and profile change after conditioning for Case I.  
Figure 13: Pad thickness and profile change after conditioning for Case II. The CMP experiment was conducted for 1 min immediately after conditioning, and the conditions of the experiment are shown in Table 4. Figure 14 illustrates the MRR distribution of the SiO\({}_{2}\) film after conditioning for Cases I (Figure 14a) and II (Figure 14b).