Deposition of Ultra Fine Aerosol Particles on Solid Surfaces

在半导体制造过程中，亚微米粒子的沉积是导致产量下降的主要原因之一。为了抑制颗粒在各种材料表面的沉积，必须很好地了解亚微米颗粒的沉积机理。本文首先利用不同材料制成的圆管，对不同荷电状态下粒子的沉积进行了实验研究。所研究的管材有铜、玻璃、聚甲基丙烯酸甲酯(PMMA)、聚氯乙烯(PVC)、聚碳酸酯(PC)和聚乙烯(PE)。结果表明：1)未带电粒子在管内以布朗扩散方式沉积；2)带电粒子在PMMA、PVC、PC和PE管内以库仑力沉积，无因次沉积速度等于带电粒子和带电无限大平板的库仑力参数。此外，从粒子…的时间依赖性的测量聚氯乙烯和聚碳酸酯管材上摩擦带电的渗透率、衰减率符合双曲线衰减规律。其次，发展了用荧光法测量直径小于0.3m的颗粒在硅片上沉积速度的实验技术。在风速0.02~0.5m/S的条件下，测量了电荷平衡粒子和直径在0.03~0.8m之间的单电荷粒子在硅片上的沉积速度，并与刘和安公式的预测值进行了比较。结果发现，Lie和Ahn方程对尺寸在0.03~0.8m之间的颗粒给出了较好的预测，当晶片和颗粒都带电时，通过将库仑漂移速度加入到他们的方程中，可以很好地估计沉积速度。此外，通过测量垂直于气流放置的晶片上的局部沉积速度，发现沉积热点出现在晶片的边缘和/或晶片的中心，这取决于晶片对气流的阻塞。较少

Deposition of submicron particles in the manufacturing process of semiconductors is one of the main causes of reducing production yield. In order to suppress particle deposition onto the surface of various materials, the deposition mechanisms of submicron particles have to be well understood. In the present work, first, by using circular tubes made of various materials, deposition of particles in various charging states was experimentally investigated. The tube materials studied were copper, glass, polymethylmetacrylate(PMMA), polyvinylchloride(PVC), pllycarbonate(PC), and polyethylene (PE). As a result it was found that 1) uncharged particle deposits by Brownian diffusion in all the tubes studies; 2) charged particle deposits in PMMA, PVC, PC and PE tubes by coulombic force, and that the dimensionless deposition velocity is equal to the coulombic force parameter derived for charged particle and charged infinite flat surface. Further, from the measurement of time dependency of particle … More penetration, decay of triboelectric charged on PVC and PC tubes was found to obey the law of hyperbolic decay. Secondly, experimental technique to measure deposition velocity onto wafer for particles with a diameter smaller than 0.3 m was developed by means of fluorometry. Employing the proposed technique, the deposition velocity onto the wafer was measured for charge equilibrium particles and singly charged particles with diameter between 0.03 and 0.8 m at airflow velocity of 0.02-0.5m/s. The measured deposition velocity was compared with that predicted by Liu and Ahn's equation. As a result, it was found that the Lie and Ahn's equation gives a good prediction for particles in the size range between 0.03 and 0.8 m, and , when both the wafer and the particles are charged, the deposition velocity is well estimated by adding the coulombic drift velocity to their equation. Further, through the measurement of the local deposition velocity on the wafer placed normal to the airflow, the deposition hot spots were found to appear on the edge of the wafer and/or at the center of the wafer, depending on the blockage of the wafer to the airflow. Less