Molecular Simulation Of Liquid Immersion Into Silica Nanoholes

In recent years, integrated circuits continue to develop with smaller and smaller dimensions. Then each chip can pack more circuits, which will increase the capacity per unit area, thereby reducing costs and increasing functionality. However, with this trend, three-dimensional interconnect faces greater challenges, one of which is how to accurately regulate the removing and filling process in the cross-scale, such as the fabrication of silica films. In addition, transport phenomena of liquid in finite-size nanopores play a significant role in many physical, biological and geological processes. Silica is an important inorganic material, which has a wide range of applications in glass, ceramics, chemicals, electronics, food, medicine and other fields. Therefore, transport phenomena of liquid in silica material have been one of the research focuses.In this thesis, molecular dynamics (MD) simulations were performed to investigate water and copper solution immersion process in silica nanoholes with five different aspect ratios. The effects of aspect ratios, numbers of water molecules and concentrations of the solution on immersion rates were analyzed. Further, the distribution of copper ions in the nanoholes was discussed.1. Water immersion process can be divided into five stages:(Ⅰ) approaching to the entrance of the hole slowly; (Ⅱ) moving into the nanohole quickly; (Ⅲ) absorbed into the deeper slowly; (Ⅳ) wetting the bottom of the hole slowly; (Ⅴ) fully filling the hole quickly. Higher aspect ratios are more beneficial to stage Ⅰ and Ⅱ but not better for stage Ⅲ and Ⅳ.2. Water immersion rates increase with the increase of aspect ratios in the system of the same number of water molecules. But, the increment decreases gradually, which implies that, aspect ratios should have no impact on water immersion rates when it reaches a certain value. Water immersion rates decrease with increasing numbers of water molecules in the system of the same aspect ratio, but the decrement declines gradually. Aspect ratios have greater influence on water immersion rate in the systems of larger numbers of water molecules.3. Copper solution immersion process has one more stage than the water immersion process:(VI) diffusion of the copper ions to the equilibrium state. Because the water molecules immersed into the nanohole prior to copper ions. The hysteresis phenomenon is more obvious than water immersion process. It keeps for a longer time with smaller aspect ratios and greater concentrations.4. Copper solution immersion rates increase with increasing aspect ratios in the system of the same concentration, but the increment declines gradually. This implies that aspect ratios should have no influence on copper solution immersion rates when it reaches a certain value. The immersion rates decrease with the increase of the concentrations in the system of the same aspect ratio. Aspect ratios and concentrations have greater impact on the immersion rate in the systems of smaller aspect ratios.5. Copper ions immersion rates do not change monotonously increasing or decreasing with increasing aspect ratios or concentrations of the solution. The concentration of copper ions near the bottom of the nanohole decreases gradually along the negative z axis, except individual aspect ratio in the systems of different concentrations. This indicates that it should be relatively difficult for the copper ions to reach the bottom of the nanoholes. But, it may be possible to select corresponding concentration of the solution for a specific aspect ratio to achieve the best filling effect according to the individual situation.