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김교선,Dong-Joo Kim,Jin-Yi Kang,Anna Nasonova,최상준 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.1
We numerically calculated the effects of pulse modulation (plasma-on and -off times) on the concentration changes of the chemical species (SiH 4 , SiH x , SiH x + and polymerized negative ions) and also the growth rate of aS i : H t h i n f i l m s i n t h e p u l s e d S i H 4 plasmas. During the plasma-on, SiH x is generated quickly by a fast dissociative reaction of SiH 4 , but, during plasma-off, SiH x disappears rapidly by a reaction with hydrogen and also by the deposition onto the reactor wall. During the plasma-on, the negative ions are polymerized by the reactions with SiH 4 , but, during the plasma-off, they disappear by neutralization reactions with positive ions. As the plasma-on time increases or as the plasma-off time decreases, the time-averaged concentrations of SiH x and negative ions and also the time-averaged film growth rate increase. This study shows quantitatively that polymerized negative ions, which are not considered to be preferred precursors for the high-quality thin films, can be efficiently reduced by the pulsed plasma process.
반도체 제조용 사일렌 플라즈마 반응기 내에서의 입자 오염에 관한 이론적 연구
김동주(Dong-Joo Kim),김교선(Kyo-Seon Kim) 한국진공학회(ASCT) 2000 Applied Science and Convergence Technology Vol.9 No.2
반도체 제조 공정 중 플라즈마 반응기 내에서 입자 오염을 유발하는 입자들의 거동과 성장을 모델 식을 사용하여 이론적으로 고찰하였다. 플라즈마 반응기 내에서 입자 거동에 영향을 미치는 힘들로 유체 대류, 입자 확산 및 외부힘 (ion drag force, electrostatic force, 중력) 등을 고려하였다. 플라즈마 벌크 영역에서 전하를 가진 입자들간의 충돌에 의한 입자 성장을 고려하기 위해 모델식에 입자 전하 분포를 고려하였다. 대부분 의 입자들은 ion drag force와 electrostatic force가 균형을 이루고 있는 두 sheath 경계 영역에 존재하였으며 두 sheath 영역과 벌크 플라즈마에서의 입자 농도는 0에 접근하였다. 시간이 지남에 따라 입자 충돌로 인한 입자들의 크기는 증가하였으며 입자가 성장함에 따라 입자 표면적의 증가와 더불어 입자가 가지는 평균 전하량도 증가하였다. We developed the model equations to investigate the particle movement and growth theoretically in a-Si plasma CVD reactor, where those particles act as the source of contamination. We included the effects of fluid convection, particle diffusion and external forces (ion drag force, electrostatic force and gravitational force) onto the particles to analyze the movements of particles in plasma reactor. Taking into account the particle charge distribution, the particle growth by coagulation between the charged particles was investigated. Most of those particles are located in the region near the sheath boundaries by the balance between the ion drag and electrostatic forces. The particle concentrations in the sheath region and in the bulk plasma region are almost zero. The sizes of the predator particles increase with time by the coagulation with protoparticles and, as a result, the surface area and the average charge of predator particles also increase with time.
TiO₂가 코팅된 Polyethylene 입자를 이용한 페놀과 톨루엔의 광분해
김동주(Kim Dong Joo),최상근(Choi Sang Keun),조준형(Cho Jun Hyung),김교선(Kim Kyo Seon) 강원대학교 산업기술연구소 2004 産業技術硏究 Vol.24 No.1
The photodegradation of phenol and toluene with the Ti0₂-coated polyethylene (PE) particles were investigated in the slurry type photocatalytic reactor, changing the Ti0₂ particle sizes, initial phenol and toluene concentrations, and the oxygen flow rate. The nano-sized Ti0₂ photocatalyst particles were prepared by the diffusion flame reactor and they were coated onto PE particles by using the hybridization system for the efficient recollection of Ti0₂- coated particles after photodegradation experiments. The degradation efficiencies of phenol and toluene with the Ti0₂-coated PE particles were more than 90% after photodegradation of 80 minutes for most cases. The efficiencies of photodegradation with the Ti0₂-coated PE particles were found to be lower than those by the pure Ti0₂ particles by 50%, because of the decrease in specific surface area of Ti0₂ particles in PE particles.
펄스 SiH₄플라즈마 화학기상증착 공정에서 입자 성장에 대한 펄스 변조의 영향
김동주(Kim Dong Joo),김교선(Kim Kyo Seon) 강원대학교 산업기술연구소 2006 産業技術硏究 Vol.26 No.1
We analyzed systematically particle growth in the pulsed SiH_4 plasmas by a numerical method and investigated the effects of pulse modulations (pulse frequencics, duty ratios) on the particle growth. We considered effects of particle charging on the particle growth by coagulation during plasma-on. During plasma-on (t_(on)), the particle size distribution in plasma reactor becomes bimodal (small sized and large sized particles groups). During plasma-off (t_(off)), there is a single mode of large sized particles which is widely dispersed in the particle size distribution. During plasma on, the large sized particles grows more quickly by fast coagulation between small and large sized particles than during plasma-off. As the pulse frequency decreases, or as the duty ratio increases, t_(on) increases and the large sized particles grow taster. On the basis of these results, the pulsed plasma process can be a good method to suppress efficiently the generation and growth of particles in SiH_(4) PCVD process. This systematical analysis can be applied to design a pulsed plasma process for the preparation of high quality thin films.