A fundamental analysis of abrasive slurry hydrodynamics in Chemical-Mechanical Polishing (CMP)

化学机械抛光（CMP）广泛应用于微电子和半导体工业。表面膜（通常只有纳米厚）是通过将芯片或晶片暴露在由悬浮在化学反应溶液中的惰性磨料颗粒组成的流动浆料中来去除的。化学组分和磨料颗粒协同作用以去除材料的表面层。CMP的两个考虑因素是材料去除率（或MRR）和表面质量（即粗糙度、划痕、凿痕、凹坑、非均匀材料去除必须最小化）。MRR和表面质量之间的平衡必须通过操纵操作条件来实现，例如磨料颗粒类型，浆料化学，抛光压力和速度。开发CMP工艺的机械模型的最大障碍之一是，将晶片与垫分离的薄膜内的浆料的流动没有很好地理解。在剪切下形成磨料颗粒聚集体可导致非牛顿浆料行为，这将显著改变浆料的流动模式、垫与晶片之间的压力分布、晶片所经受的剪切应力以及与表面接触的颗粒的速度和浓度。拟议的研究计划将建立在实验多相流和机械磨损的主要研究者的专业知识。拟议的研究计划的主要目标是开发一个新的和更严格的理解在CMP过程中的浆料流的流体力学，并显示流体力学，磨粒性能，浆料流变学，垫压力和它们的综合影响的机械方面的材料去除率和表面质量之间的相互联系。Micro-PIV（粒子图像测速）和浆料流变测量将同时在一个新的，定制设计的测试装置，直接研究速度场和颗粒聚集之间的关系。 额外的微型PIV实验将使用一个实验室规模的CMP机，使垫粗糙度和磨料颗粒聚集的速度和剪切场的影响，在抛光过程中可以确定。最后，将测试为特定流体动力学条件设计的聚合物复合颗粒，并将其设计为使剪切诱导的聚集最小化。该计划的结果对所有CMP研究人员和从业人员来说都是非常宝贵的，因为浆料流动流体动力学确实是化学抛光动力学和机械磨损之间的联系。微电子行业将能够使用这些结果来预测CMP性能并优化其操作，而无需使用当前的试错方法。

Chemical-mechanical polishing (CMP) is widely used in the microelectronics and semiconductor industries. Surface films (often just nanometers thick) are removed by exposing the chip, or wafer, to a flowing slurry consisting of inert abrasive particles suspended in a chemically reactive solution. The chemical components and the abrasive particles work synergistically to remove a surface layer of material. The two considerations for CMP are material removal rate (or MRR) and surface quality (i.e. roughness, scratches, gouges, pits, nonuniform material removal must be minimized). A balance between MRR and surface quality must be attained by manipulating operating conditions, e.g. abrasive particle type, slurry chemistry, polishing pressure and velocity. One of the greatest impediments to the development of a mechanistic model of the CMP process is that the flow of the slurry within the thin film separating the wafer from the pad is not well understood. Formation of abrasive particle aggregates under shear can cause non-Newtonian slurry behavior, which will substantially alter the flow pattern of the slurry, the pressure distribution between the pad and the wafer, the shear stresses experienced by the wafer, and the velocity and concentration of particles coming into contact with the surface. The proposed research program will build upon the expertise of the principal investigator in experimental multiphase flows and mechanical abrasion. The main objective of the proposed research program is to develop a new and more rigorous understanding of the slurry flow hydrodynamics in a CMP process and to show the interconnectivity among hydrodynamics, abrasive particle properties, slurry rheology, pad pressure and their combined effect on the mechanical aspects of material removal rate and surface quality. Micro-PIV (particle image velicometry) and slurry rheology measurements will be made simultaneously in a novel, custom-designed test apparatus to study directly the relationship between velocity field and particle aggregation. Additional micro-PIV experiments will be done using a bench-scale CMP machine so that the effects of pad asperities and abrasive particle aggregation on the velocity and shear fields during a polishing event can be determined. Finally, polymer composite particles designed for specific hydrodynamic conditions, and designed to minimize shear-induced aggregation, will be tested. The results of this program will be invaluable to all CMP researchers and practitioners because the slurry flow hydrodynamics really are the link between the kinetics of chemical-based polishing and mechanical abrasion. The microelectronics industry will be able to use these results to predict CMP performance and optimize their operations without using the current trial-and-error approach.**