# Hybrid CMP Slurry Supply System Using Ionization and Atomization
## 3 Results
### Step Height Reduction and Dishing during CMP of Patterned Wafers  
Figure 7 compares the 2D surface profiles of the patterns obtained in the die after the completion of the CMP processes in the conventional and hybrid systems. The average initial step height of the patterns before applying CMP was approximately 490 nm. As indicated in the figure, the hybrid system achieved planarization earlier than the conventional system. The result of the hybrid system at 30 s was similar to that of the conventional system, this is because the system is in a transient state and polishing does not occur properly in this short time. The step height difference between the conventional and hybrid systems was approximately 100 nm after 60 s. Therefore, the processes of the two systems attained a steady-state with a constant MRR as indicated by the rate of the step height reduction. Ideally, the material-removal mechanism of the PW must remove the materials only from the top of the step (upper layer), resulting in global planarization. However, polishing occurs simultaneously on the upper and lower layers in an actual CMP process. Thus, despite the same process conditions, the calculated MRR is different from the previously obtained results (Figure 5). In addition, the step height decreases at a faster rate when the pitch size is small regardless of the type of the slurry supply system. [PERSON] et al. (2017) reported that only those pad asperities with radii of curvatures of less than 7 mm at a 5 mm trench width were in contact with the lower layer. This indicates that the contact area between the pad and the lower layer is less when the trench width is small.  
To verify the effect of the hybrid slurry supply system, Figure 8 illustrates the average step height reduction as a function of the process time using the patterns of two pitch sizes. As indicated in the figure, the hybrid system completes the polishing process in a shorter time than the conventional system. Thus, the hybrid system can reduce the processing time in the case of patterned CMP. Based on the preliminary results, we determined the CMP endpoints for both systems. While the hybrid system revealed the patterns in a process time of 3 min 20 s, the conventional system performed the same process in 4 min 20 s.  
Figure 9a illustrates the dishing observed in the conventional system owing to the step height of the Cu loss. We ceased the CMP process after the endpoint detection, and the amount of dishing was 24 nm and 21 nm in the conventional and hybrid systems, respectively, before over-polishing occurred. Figure 9 illustrates the results of the Cu dishing based on the process of over-polishing. As indicated in the figure, the Cu dishing turns severe as the over-polishing progresses regardless of the slurry supply system.  
The Cu dishing in the hybrid system was 5%-28% less than that of the conventional system. As the over-polishing progressed, the dishing reduction effect of the hybrid system increased. As illustrated in Figure 10, the hybrid system can reduce the pitch dependence in the 10-30% of over-polishing.  
Figure 11 depicts the process temperatures of both the hybrid and conventional systems. As indicated in the figure, the temperature of the hybrid system was significantly lower than that of the conventional system. This is because the wide coverage of the atomized slurry and gas influences the pad temperature significantly. Additionally, this cooling effect primarily causes the reduction in dishing. Moreover, it prevents heat accumulation between the CMP processes.  
Figure 7: The 2D patterns of the surface profiles at 200- and 100-\(\upmu\)m pitches. (**a**) The conventional system and (**b**) the hybrid system.  
Figure 8: Average step height based on the process time. The effect of the hybrid system is verified at 200- and 100-\(\upmu\)m pitches.  
Figure 9: Dishing depth based on the over-polishing time. (**a**) The conventional system and (**b**) the hybrid system.