## 3 Results
### Experiment
#### 3.2.3 Conditioning Effects According to Pad Temperature  
Figure 10a shows the results regarding the increase in the material removal rate according to the temperature during the conditioning process. The experiment used pads that underwent long-term polishing and glazing without a conditioning process. To set the temperatures of the pads during conditioning at 4 levels (26, 42, 58, and 69 degrees) deionized water at suitable temperatures was provided. Temperature errors of 1-2 degrees occurred at each temperature during processing. In each case, when the polishing process was performed directly after conditioning, it was found that the material removal rate increased proportionally as the pad temperature increased during conditioning [23]. The highest material removal rate increase occurred at 58 \({}^{\circ}\)C and trended downward at 69 \({}^{\circ}\)C. Figure 10b shows a graph of the asperity angles at each pad temperature. As with the increase in the material removal rate, the asperity angles likewise increased linearly in proportion to the temperature. Thus, it was found that the asperity angles changed according to the pad temperature in the conditioning process as well, and this may have a positive effect on restoring the material removal rate of worn pads. However, at excessively high temperatures such as 69 \({}^{\circ}\)C, the material removal rate decreased regardless of the angles of the asperities. This is believed to be caused by the increase in pad residue that occurs during high-temperature conditioning and the resultant clogging of the pores. Figure 10: (**a**) Increase amount of material removal rate and (**b**) asperity angle according to pad temperature during the conditioning process. Figure 9: Schematic images of the change of the asperity angle according to the pad surface temperature during continuous CMP without conditioning. To confirm that the asperity angles had genuinely changed, various methods of measurement were used to establish the reliability of the findings, with the results as shown in Figures 11 and 12. Figure 11 shows SEM images of the pad surface when one cycle of the CMP process was performed immediately after conditioning at different pad temperatures. When polishing was performed continuously without conditioning and the pad became worn, the surface was so flat that it was difficult to distinguish the shapes of asperities and pores. As the conditioning process progressed, the surface became rough, and the contours of the asperities were seen. In low-temperature conditioning, it was found that the asperities were highly inclined. In addition, the pores were not perfectly spherical, and they were hidden by the asperities. As the pad temperature increased, however, it was found that the asperity angles also increased. By looking at the front face, it was found that there were definite asperities and that the pores formed perfect spheres. Figure 12 is a image showing the surface roughness for each process condition using a micro-CT measurement. This results also show similar phenomenon. It shows the results of using a micro CT to examine the surface and cross-section shapes when different conditioning temperatures were applied to the same pad. At the lower temperature (26 \({}^{\circ}\)C), most of the pores are blocked by asperities, but at the higher temperature (69 \({}^{\circ}\)C), the shapes of the pores are clearly seen. In addition, the contact surface profile measurement device was used to examine surface characteristics according to the angles of the asperities. Figure 11: SEM images of pad surface according to pad temperature during the conditioning process (captured immediately after one cycle of the polishing process at four temperatures: 26, 42, 58, and 69 \({}^{\circ}\)C). Figure 12: Micro-CT surface and cross section measurements examining asperity angles and pore exposure after low and high temperature conditioning processes.