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실험 및 유한요소해석에 의한 SU-8 박막의 Tribological 특성 연구
양우열(Woo Yul Yang),신명근(Myounggeun Shin),김형만(Hyung Man Kim),한상철(Sangchul Han),성인하(In-Ha Sung) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.4
본 연구에서는 SU-8 박막의 마이크로시스템으로의 트라이볼로지적 응용을 목적으로 하여, 원자간 힘 현미경(AFM) 과 콜로이드 프로브를 이용한 실험 및 유한요소해석 기법을 이용하여 SU-8 코팅층의 두께에 따른 트라이볼로지적 특성을 고찰하였다. SU-8 시편은 스핀 코팅기법을 이용하여 두께를 다르게 하여 제작하였다. 실험결과 코팅두께가 증가함에 따라 마찰력과 점착력이 감소하여 박막두께에 따른 차이가 존재함을 알 수 있었고, SU-8 표면이 Si 표면에서보다 더 낮은 점착력과 마찰력을 보여주었다. 또한, 시뮬레이션을 통해 두께별로 박막 파손을 유발시키는 임계하중(압력)이 존재하며, 본 연구에서의 200~800 nm 두께범위에서는 1.2~1.8 GPa 로 측정되었다. In this study, two-dimensional finite element models were developed and experiments were conducted using an atomic force microscope to investigate the tribological characteristics of an SU-8 layer coated on a patterned wafer for microsystem applications. The results revealed that both the adhesion and the friction forces measured by the atomic force microscope were lower for the SU-8 coated surface than for the bare silicon surface. This is attributed to the hydrophobicity of SU-8. Another important result derived from the finite element analysis was the critical load required to fracture the SU-8 film with respect to the thickness. The critical loads for thicknesses of 200, 400, and 800 nm were approximately 13, 22, and 28 mN, respectively, which corresponded to a Hertzian contact pressure of 1.2?1.8 GPa. These results will aid in the design of a suitable SU-8 thickness for microsystem components that are in contact with one another.
입자연마가공에서의 압력 속도 및 유체점도의 영향에 대한 고찰
양우열(Woo Yul Yang),양지철(Ji Chul Yang),성인하(In-Ha Sung) 한국트라이볼로지학회 2011 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.27 No.1
Interest in advanced machining process such as AJM(abrasive jet machining) and CMP(chemicalmechanical polishing) using micro/nano-sized abrasives has been on the increasing demand due to wide use of super alloys, composites, semiconductor and ceramics, which are difficult to or cannot be processed by traditional machining methods. In this paper, the effects of pressure, wafer moving velocity and fluid viscosity were investigated by 2-dimensional finite element analysis method considering slurry fluid flow. From the investigation, it could be found that the simulation results quite corresponded well to the Preston's equation that describes pressure/ velocity dependency on material removal. The result also revealed that the stress and corresponding material removal induced by the collision of particle may decrease under relatively high wafer moving speed due to the slurry flow resistance. In addition, the increase in slurry fluid viscosity causes the reduction of material removal rate. It should be noted that the viscosity effect can vary with the shape of abrasive particle.
CMP 공정에서의 웨이퍼 연마 불균일성에 대한 유한요소해석 연구
양우열(Woo Yul Yang),성인하(In-Ha Sung) 한국트라이볼로지학회 2012 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.28 No.6
Finite element analysis was carried out using wafer-scale and particle-scale models to understand the mechanism of the fast removal rate(edge effect) at wafer edges in the chemical-mechanical polishing process. This is the first to report that a particle-scale model can explain the edge effect well in terms of stress distribution and magnitude. The results also revealed that the mechanism could not be fully understood by using the waferscale model, which has been used in many previous studies. The wafer-scale model neither gives the stress magnitude that is sufficient to remove material nor indicates the coincidence between the stress distribution and the removal rate along a wafer surface.