## 3 Results
### Experiment
#### 3.2.2 Continuous CMP Runs According to Pad Temperature  
As mentioned in the introduction section, the asperities of the pad induce direct contact between the slurry particles and the wafer, and the pores increase the flow of the slurry and act as a trap to store the polishing residue. Especially in the oxide CMP, since the oxide film can be removed by mechanical contact compared to the chemical effect, the asperities and pores developed on the pad surface act advantageously and enhance the Material removal rate(MRR) [22]. In this study, in order to investigate these phenomena more clearly, the change in the angle of the asperities according to the temperature during the CMP process was observed. A series of CMP experiments, each for 1 min, were performed continuously with funnel silica slurry on a break-in pad without conditioning process, as shown in Figure 7a. It could be observed that the removal rate gradually decreased as the CMP process progressed under three pad temperature conditions. The removal rate considered to be additionally necessary for the conditioning process was set to 140 nm/min. After certain runs (42 \({}^{\circ}\)C, 5 th run; 55 \({}^{\circ}\)C, 12 th run; 69 \({}^{\circ}\)C, 18 th run), the removal rate tended to be very low. Even within these trends, when the pad temperature was high during this CMP process, the removal rate was higher, and the reduction rate of the removal rate was low relative to that at the lower temperatures. In addition, when the removal rate in the range of 140 nm was obtained for each condition, the conditioning process was performed, and it was confirmed that the removal rate and the asperity angle were recovered. From Figure 7b, it can be seen that the pattern of the asperity angle at this time is similar to the pattern of the removal rate. Thus, this investigation of the relationship among pad temperature, removal rate, and asperity angle found that the tendency for the asperity angle to increase has a positive effect on the contact with the wafer and further influences the MRR. Figure 6: Illustration of (**a**) continuous CMP process experiment with temperature control (without conditioning) and (**b**) conditioning effect experiment with temperature control. Figure 8 shows SEM images of the pad surface after the CMP process at three pad temperatures. For each temperature, it can be seen that the asperity angle was somewhat increased on the pad surface in the initial CMP run. Similar to the asperity angle results in Figure 7b, the pad surface image also showed an elevated asperity angle at high temperatures. At lower temperatures, however, the asperities were inclined and pressed for a relatively short time, whereas at the higher temperatures, the asperity angle was maintained for a longer run time, and pores remained even in the state in which the pad was glazed. It can be inferred that this is because at low temperatures, the asperities are simply subjected to pressure, whereas at higher temperatures, they are subjected to pressure and at the same time the angle is increased, and pores at the bottom are exposed. The increase in pores that was seen during high-temperature polishing causes an increase in the slurry flow and traps a large amount of the residue that is created during polishing. Therefore, this experiment found that an increase in asperity angle and an increase in pore formation at high temperatures may increase the polishing rate and delay pad wear. Figure 8: Pad surface SEM images of pad surface according to pad temperature in a continuous CMP polishing process without a conditioning process. Figure 7: (**a**) Material removal rate trend and (**b**) the angles of the asperities according to the pad temperature during a continuous CMP polishing process without a conditioning process. The schematic of asperity change on the pad surface in a continuous polishing process can be represented as shown in Figure 9. In the polishing process, the pad is pressed by the polishing load.