Doyun An

This study presents a comprehensive three-dimensional unsteady computational fluid dynamics (CFD) investigation into the transient slurry transport mechanisms within a 300 mm silicon dioxide (SiO2) chemical mechanical polishing (CMP) system. The numerical model incorporates realistic pad groove geometries and detailed retaining ring slots to accurately capture slurry flow. Six simulation cases were analyzed under varying platen/head rotational speeds and slurry flow rates. Results indicate that accelerated pad rotation induces significant centrifugal thinning of the slurry film, while increased flow rates facilitate a broader radial footprint of slurry near the intake. Slurry recirculation zones were observed within the wafer-pad gap, decreasing in intensity at higher velocities. Furthermore, the simulations established a robust spatial correlation between the predicted slurry volume fraction and experimental material removal rates (MRR). These insights provide a physical basis for optimizing slurry delivery efficiency and mitigating within-wafer non-uniformity (WIWNU) in advanced semiconductor manufacturing processes.

This study investigates the unsteady dispersion characteristics of hydrogen jets under varying flow velocities and inert gas purging conditions using computational fluid dynamics (CFD). Simulations were performed for six cases with identical total hydrogen mass release but different jet velocities and nitrogen purging conditions. A two-dimensional axisymmetric domain and the SST k-ω turbulence model were employed to predict transient concentration fields and jet behavior. Results show that higher jet velocities extend jet penetration and enhance initial mixing, leading to a wider flammable region near the nozzle, but also accelerate subsequent dilution. After hydrogen release stops, buoyancy dominates jet dispersion, causing residual hydrogen to accumulate in upper regions. Nitrogen purging effectively reduces hydrogen concentrations below the lower flammability limit more rapidly by displacing hydrogen and enhancing entrainment. These findings provide quantitative insights into hydrogen jet dispersion and offer practical implications for safety assessment and mitigation in high-pressure storage systems.

To analyze the flow and noise characteristics of a positive displacement hydrogen compressor, a computational fluid dynamics (CFD) simulation based on the Lattice-Boltzmann Method (LBM) was performed. For detailed analysis the discharge flow of the compressor was divided into three regions: the area around the valve, the discharge jacket, and the outlet pipe. Hydrogen passing through the valve formed turbulent jets, which induced high-frequency noise. Inside the discharge jacket, changes in the cross-sectional area caused continuous variations in the average velocity and turbulence characteristics. In the outlet pipe with an elbow, high flow velocity corresponding to the relatively narrow cross-section was observed. Additionally, flow separation occurring on the inner corner of the elbow enhanced turbulence, contributing to the amplification of high-frequency noise. This study provides a physical understanding of the flow and noise issues in positive displacement hydrogen compressors and presents a fundamental analysis to support the design of efficient and low-noise compressors.