Hoomi Choi

In-Situ Measurements of Charged Nanoparticles Generated During Hot Wire Chemical Vapor Deposition of Silicon Using Particle Beam Mass Spectrometer

It has been experimentally confirmed in many chemical vapor deposition (CVD) processes that charged nanoparticles tend to be generated in the gas phase. In an effort to confirm and measure charged gas phase nuclei, that might be generated during the deposition of Si thin films by hot wire CVD, we performed an in-situ measurement using particle beam mass spectrometer (PBMS), which can measure a size distribution of nanoparticles at low pressure. The size distribution of positively and negatively charged Si gas phase nuclei generated during hot wire CVD under 1.5 torr could be firstly measured. The particle diameter at the peak of the size distribution is about 10 ∼ 13 nm. At a wire temperature of 1800°C, the number concentration of negatively charged Si nanoparticles was higher than that of positively charged ones. The size and number concentration of charged nanoparticles decreased with increasing wire temperature from 1800 to 2000°C and increased with increasing SiH4 concentration from 3 to 6%. Copyright 2013 American Association for Aerosol Research

Numerical Simulation of Ultrasonic Generator in Dust Removing System

An ultrasonic dry cleaning system is a kind of air-blowing cleaning system, which clears away fine particles of dust adhering to a surface. This system does not require high cost consumables such as highly pure gases or chemical solvents. Moreover it removes micro contaminant particles without additional cooling or heating processes. In this paper, a numerical simulation of the ultrasonic dry cleaning system was carried out to propose an optimum ultrasonic generator. We evaluated the flow in the chamber according to the groove shape of ultrasonic generator, and system operating pressure using a commercial fluid dynamic simulation tool. And the trend of the sound pressure level (SPL) according to frequency was checked to determine whether or not the ultrasonic generator module could generate an ultrasonic wave. The particle trajectories were compared for several conditions and particle sizes. We confirmed that an ultrasonic wave of sufficient flow velocity can be generated through the ultrasonic generator module. And the changes of SPL according to the system operating pressure and the shape of the ultrasonic generator groove were confirmed respectively.

Optimization of CO2 Gas Cluster Generation for Cleaning Application

cleaning application Hoomi Choi, Hojoong Kim, Deokjoo Yoon, Jong W. Lee, Bong-Kyun Kang, Min-Su Kim, Jin-Goo Park, Taesung Kim SKKU Advanced Institute of Nanotechnology (SAINT) School of Mechanical Engineering Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon, Gyeonggi, Korea R&D center, ZEUS Co.,Ltd., 163-1 Busan-dong, Osan, Gyeonggi, 447-050, Korea Department of Materials Engineering, Hanyang University, Ansan, 426-791, Korea

Nano Gas Cluster Dry Cleaning for Damage Free Particle Removal

This work has been partially supported by the Research Center for Integrated Human Sensing System and Post BK21 program. Gas cluster cleaning system was supported by Zeus Co.LTD, Korea