Papers by Keyword: Solid-Liquid Interface

Abstract: As miniaturization progresses, pattern collapse during the drying step of wet cleaning processes has become a critical issue in the semiconductor industry. In this study, we used reactive molecular dynamics simulations to analyze pattern collapse, with a focus on bondings and reactions. To simulate pattern deformation during the drying process of wet cleaning, we created a FinFET model as a HAR structure. The surface of this model was terminated with hydrogen atoms. The widths between the patterns were changed in order to create a Laplace pressure difference when water molecules were placed on the surface. The model was simulated by placing water molecules up to half the height of the pattern. As a result, the pattern was deformed. Furthermore, by removing water molecules and changing the Laplace pressure balance, it was found that the pattern contacted each other at the tip. The pattern remained in contact when water molecules were removed from the model. In the contact area, the covalent bonds, such as Si-Si and Si-O-Si, were not formed, but instead, hydrogen-to-hydrogen van der Waals bonds were formed between patterns. We calculated the total van der Waals forces between hydrogen atoms at the contact surfaces using the Hamaker equation and calculated the elastic force of the patterns using the beam deflection formula. Our calculations showed that the total van der Waals forces between hydrogen atoms at the contact surfaces were larger than the elastic force of the patterns, indicating that van der Waals forces could be a factor in maintaining the contact of the patterns.

Abstract: Wet etching in nanometer-sized three-dimensional spaces creates new challengesbecause of the scaling of semiconductor devices with complex 3D architecture. Wet etching withinspaces is affected by the mass transport of the etchant ions that are impacted by the hydrophobicityand surface potential of surface. However, the kinetics of chemical reactions within the spaces is stillunclear.In this paper, we studied the effect of hydrophobicity and surface potential of silicon surface on SiO2etching in nanometer-sized narrow spaces by adding various additive components to etching solutions.We found that the transport of etchant ions into narrow spaces is governed by controlling thehydrophobicity and surface potential of the confined system walls.

Abstract: The problem of a planar solidification of a material with an additional nonstationary radiant of heat on a semi-infinite plane has been solved. For a solution the condition of Stefan was used. Results have been compared with an analytical solution in case of the absence of an additional radiant of heat, as well as with a solution obtained by perturbations method. A more complicated two-dimensional nonstationary problem of a solidification of a liquid with interface free-boundary has been also solved. The purpose of this problem solution is to predict position of a material phase boundary, as well as the temperature distribution in a layer of PCM (Phase-Change Material) with boundary conditions of Dirichlet.

Abstract: The microminiaturization of semiconductor devices has made it necessary to control the wet etching process on the nanometer order. It is therefore extremely important to understand wet etching reactions in the nanoscale region of solid-liquid interfaces, in order to assist in optimizing process conditions to satisfy the severe demand for semiconductor devices. Simulations performed to analyze the behavior of liquid molecules in the nanoscale region have been reported ^[1], but there have been few reports of detailed experimental results. We here report detailed experimental results on the wet etching behavior of SiO₂ film in the nanoscale region between Si materials.

Abstract: Faceted growth of primary Al₃Ni phase in the hypereutectic Al-Ni alloy in a high magnetic field was investigated. It was found that faceted growth of primary Al₃Ni phase was enhanced in the presence of the magnetic field. However, the fibrous to granular transition of Al-Al₃Ni eutectics occurred. The undercooling of primary and eutectic phases during solidification was measured using differential thermal analysis. It was showed that the undercooling of primary phase was hardly changed but that of eutectics markedly increased in the magnetic field. According to Cahn theory of crystal growth, the critical driving force was used to satisfactorily explain the morphology transition in the magnetic field.

Abstract: Simulation of nanoscale thermo-fluidic transport has attracted considerable attention in recent years owing to rapid advances in nanoscience and nanotechnology. The three- dimensional molecular dynamics simulations are performed for the system of a liquid layer between two parallel solid walls at different wall temperatures. The solid-solid interaction is modeled by the embedded atom method. The heat flux through the solid-liquid interface is calculated by Green-Kubo method. The effects of interface wettability and wall temperature on the interfacial thermal resistance are also analyzed. It is found that there exist the relatively immobile quasi-crystalline interfacial layers close to each solid wall surface with higher number density and thus higher local thermal conductivity than the corresponding liquid phase. The interfacial thermal resistance length is overestimated by 8.72% to 19.05% for the solid-solid interaction modeled by the Lennard-Jones potential, and underestimated based on heat fluxes calculated by Fourier equation.

Abstract: The effect of the position and shape of solid-liquid interface on process parameters has been studied by the numerical simulation method, and the reasonable process parameters have been given. The results shows that the position and shape of solid-liquid interface is mainly affected by mold temperature, casting speed and cooling distance. It were moved to the mold export with the improvement of the mold temperature, casting speed or the reduce of cooling capacity. And the reasonable process parameters are that the mold temperature is 1363-1373 K, casting speed is 80-100mm/min, cooling distance is 40-50mm. The research results would obtain stable operation conditions and improve the billet quality.

Abstract: This paper deals with the interaction mechanism between in situ Nb₂C-V₂C nanoparticles and solid/liquid interface during the rapid solidification of Fe-Nb-V alloy ribbons. In situ Nb₂C-V₂C nanoparticles reinforced Fe alloy matrix composite were carried out by in situ reaction and melt spun with a high-speed centrifugal spray. According to the setting of a force balance for the in situ nanoparticles in front of the S/L interface during the high-speed centrifugal spray of Fe-Nb-V alloy melt as following: F = F_{buoyant force} + F_repulsive + F_{viscous force} + F_{centrifugal force}, authors get the critical velocity that S/L interface engulfs particles is proportional to the radius of particles. TEM observation indicates that the less the size of particle is, the more easily S/L interface engulfs particles.

Abstract: Mercury-stannum reactive wetting behaviors were studied by the sessile drop technique at room temperature, and wetting surface and interface were also studied respectively by methods of field emission scanning electron microscope (FESEM) and XRD. It showed that mercury droplets wetted completely on the stannum substrate, on whose surface up-and-down cellular structures were generated, and two metallographic microstructures of intermetallic compounds, Hg_0.1Sn_0.9 and Hg_1.25Sn_8.75, were produced in wetting interface.

Abstract: A new algorithm of phase field model is developed to simulate polycrystalline dendritic solidification growth in undercooled melts. The algorithm adopts a single phase field order parameter model incorporated with the anisotropy of solid-liquid interfacial energy and mobility. The model validation is performed by comparing the simulations with the theory analytical results and experimental information for both single and multi-grain dendritic growth, which demonstrates the quantitative capabilities of the proposed algorithm.