# Hybrid CMP Slurry Supply System Using Ionization and Atomization
## 4 Discussion
Thus, the ionized slurry improves the chemical reactivity generating a thicker reaction layer of low hardness, which improves the MRR. The atomization system improves uniformity owing to the uniform supply of slurry and the reduced deviation in the pad temperature distribution. The particles involved in the polishing process influence the material removal process significantly [2]. The spray slurry nozzle atomizes and supplies the ionized slurry to the pad with wide coverage. The abrasives participating in the polishing are distributed uniformly at the wafer-pad interface [25]. Moreover, the pad temperature distribution has a significant influence on uniformity [2; 26]. The uniformity can be improved by reducing the temperature distribution deviation in the radial direction of the pad using the atomized slurry and gas. Furthermore, it serves as a cooling system that cools the pad through active heat transfer as the slurry is distributed thinly and widely on the pad and the gas is supplied with the slurry. Furthermore, the variations in temperature influence the Cu fishing significantly; the fishing decreases with the temperature [27; 28]. Therefore, the pad temperature decreases owing to the cooling effect of the hybrid system, and the fishing and heat accumulation can be reduced. Also, fishing is affected by the MRR difference between Cu and SiO\({}_{2}\). When the hybrid system was used in Cu CMP and SiO\({}_{2}\) CMP, MRR increased 23% and 39%, respectively (Figures 5 and 6). Also, when comparing the value of the MRR in SiO\({}_{2}\) CMP divided by the MRR in Cu CMP between the conventional system and hybrid system, they were 0.306 and 0.346, respectively. When using a hybrid system, it can be seen that the  
Figure 12: Comparison of conceptual illustrations between the (**a**) conventional and (**b**) ionized slurry. MRR of Cu is relatively decreased compared to that of SiO\({}_{2}\). Therefore, Cu loss is reduced during over-polishing, resulting in reduced fishing. In addition, the atomization system increases the MRR. The slurry atomized by the spray slurry nozzle has a wider coverage than the tube nozzle at the same flow rate and is distributed widely on the pad surface to form a thin slurry film (Figure 1). Because of this, the bow wave, which is a phenomenon in which the slurry cannot participate in the polishing and is stagnant at the leading edge of the carrier, decreases. Thus, the number of particles participating in the polishing increases owing to the decrease in the bow wave height [29]. Furthermore, the slurry is distributed relatively wider and uniformly at the wafer-pad interface compared to the conventional system. The overall slurry film thickness becomes thinner, and frictional force increases due to change in lubrication condition (Figure 14). As a result, the MRR increases due to the increase in particles involved in the polishing process and increase in frictional force. Figure 14: The frictional force and slurry film thickness. Both the factors are expressed as a function of fluid viscosity and velocity divided by the load. Figure 13: Load-indentation depth curves for surfaces etched by slurries with different AC power strengths. The indentation occurred at a maximum load of 0.2 mN.