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

由于CMP工艺中使用的浆料含有几种化学添加剂，因此在某些条件下，浆料中的颗粒可能在抛光工艺之前和期间聚集并粘附到晶片和/或垫表面。这种聚集导致缺陷，例如晶片表面上的划痕。因此，对于没有故障的良好的局部和全局平面性的性能，重要的是确定用于制备没有聚集体的稳定浆料的最佳条件。此外，在该过程中获得关于骨料的尺寸和形状的正确知识，即，在晶片和垫之间的受限剪切流中颗粒的聚集和破碎行为也是关键问题。本文旨在从理论和实验两方面研究两平行壁面间简单剪切流中的颗粒动力学， 关于我们 在两个平行圆盘之间的剪切流中原位观察颗粒动力学。实验中，将直径为2μm的聚苯乙烯颗粒悬浮在NaCl水溶液中。我们可以观察到剪切流中聚集体的旋转行为。结果发现，较低的剪切速率导致较大尺寸的聚集体。另外，随着圆盘间距的增大，聚集体的平均面积增大。在该模型中，我们考虑了流体阻力，颗粒与颗粒之间的相互作用，颗粒与壁面之间的相互作用，以及胶体之间的相互作用。随着平行壁间距的增大，团聚体的粒径增大，与壁面接触的团聚体数量减少。当颗粒与壁面间的相互作用小于颗粒与颗粒间的相互作用时，聚集体的尺寸增大，与壁面接触的聚集体数量减少。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