[SY-K3] Symposium K-3

[SY-K3] Effects of Shockwave-Induced Nanobubble Collapse on Precision Polishing : Molecular Dynamics Study

^○yoshimasa aoyama¹, Jingxiang Xu², Yuske Ootani¹, Nobuki Ozawa¹, Momoji Kubo¹ (1.Dept. of Materials Science, Tohoku Univ., Japan, 2.Dept. of Mechanical Engineering, Shanghai Ocean Univ., China)

Chemical mechanical polishing (CMP) is used for the planarization of semiconductor materials. However, some of them are much hard. Therefore, the designing of efficient CMP process of hard materials is required. In order to achieve an efficient CMP process, we focused on a nanobubble. When the nanobubble collapses, the liquid around the bubble forms a jet which creates a water hammer shock. Therefore, we suggested that applying the jet increases the efficiency of CMP process. To establish the efficient CMP, revealing the effects of the nanobubble collapse on precise polishing is required. In order to reveal the effects of the nanobubble collapse on a solid surface, we performed nanobubble collapse simulation on a solid surface by molecular dynamics method. First, we made the nanobubble in water solvent by removing the solvent molecules spherically. Next, we applied shockwave and performed nanobubble collapse simulation on the solid surface. In order to clarify the effects of one nanobubble collapse, we compared the nanobubble collapse simulations and only shockwave simulation. In the nanobubble collapse simulation, a jet was generated by the nanobubble collapse and the structural change in the solid surface was larger compared with the shockwave simulation. This suggests that a nanobubble would be useful to increase the removal rate of a solid surface. Next, in order to clarify the effects of different number of nanobubbles, we compared the nanobubble collapse simulations with one and two nanobubbles. We found that the structural change by the two nanobubbles simulation was larger than that by the one nanobubble simulation. When the jet passes the water solvent, the stream of the jet decays. However, when the generated jet passes another nanobubble, the stream of the jet does not decay, because there are no water molecules in the nanobubble. Therefore, increasing the number of nanobubbles would be useful to improve the removal rate.