Experimental and Theoretical Studies on Particle Dynamics in Chemical Mechanical Polishing (CMP) Process

由于化学机械抛光过程中使用的浆料含有几种化学添加剂，在一定条件下，浆料中的颗粒在抛光过程之前和过程中可能会聚集并附着在晶片和/或焊盘表面。这种聚集会导致晶片表面出现划痕等缺陷。因此，为了无故障地获得良好的局部和全局平整度，重要的是确定制备无团聚稳定浆料的最佳条件。此外，获得有关过程中聚集体的大小和形状的正确知识，即在晶片和衬垫之间的受限剪切流中粒子的聚集和破碎行为，也是一个关键问题。本工作的目的是从实验和理论上研究两个平行壁间的简单剪切流动中的颗粒动力学。我们为…研制了一台带有共焦扫描激光显微镜的实验装置两平行圆盘间剪切流动中颗粒动力学的更多现场观测。在实验中，将直径为2μm的聚苯乙烯颗粒悬浮在氯化钠水溶液中。我们可以观察到剪切流中集合体的旋转行为。结果发现，剪切速率越低，聚集体的尺寸越大。另外，随着圆盘间距的增大，聚集体的平均面积增大。建立了剪切流中颗粒聚集过程的数学模型。在该模型中，我们考虑了流体阻力、颗粒与颗粒、颗粒与壁面的相互作用以及胶体相互作用。随着平行壁间距离的增大，聚集体的尺寸增大，与壁面接触的团聚体数量减少。当颗粒与壁面之间的胶体相互作用小于颗粒与颗粒之间的胶体相互作用时，聚集体的尺寸增大，与壁面接触的聚集体数量减少。较少

Since the slurries used in the CMP process contain several chemical additives, under certain conditions, the particles in the slurries may aggregate and adhere to the wafer and/or pad surfaces before and during the polishing process. Such aggregations result in defects such as scratches on the wafer surface. Therefore, for performance of good local and global planarity without failures, it is important to determine the optimal conditions for preparation of stabilized slurries without aggregations. In addition, the acquirement of correct knowledge about the size and shape of aggregates during the process, i.e., the aggregation and breakage behaviors of particles in a confined shear flow between the wafer and the pad, is also a critical issue. The aim of the present work is to investigate experimentally and theoretically the particle dynamics in a simple shear flow confined between the two parallel walls.We developed an experimental apparatus with a confocal scanning laser microscope for … More in-situ observation of the particle dynamics in a shear flow between two parallel disks. In experiment, polystyrene particles of 2μm in diameter were suspended in a NaCl aqueous solution. We could observed the rotational behavior of aggregates in a shear flow. As a result, it was found that lower shear rate results in larger size of aggregates. In addition, as the distance between two disks increased, the average area of aggregates increased.We constructed a mathematical model for particle aggregation process in a shear flow. In this model, we considered the hydrodynamic drag, the interaction between particle and particle, and particle and wall, and colloidal interactions. As the distance between two parallel walls increased, the size of aggregates increased and the number of aggregates contacted with wall decreased. When the colloidal interaction between particle and wall was smaller than that between particle and particle, the size of aggregates increased and the number of aggregates contacted with wall decreased. Less