패드 단일미세접촉점에서의 화학적 기계연마 공정 분석

Abstract

Chemical Mechanical Polishing (CMP) is widely used for semiconductor chip manufacturing for several decades. However, due to the process complexity including the involvement of contact mechanics in different length scales, from nanometer sized abrasives, micrometer sized pad asperities, to the millimeter sized wafers, CMP yet remains as an unpredictable process and therefore heavily depends on empirical parameters [refs1]. In addition, the irregular top surface of polishing pads, which is one of the key components delivering the necessary polishing force to the abrasives for the nano-scale polishing, hinder our understanding of CMP process physics [refs2]. Here, we develop methods to fabricate micro-asperities with well-defined geometry and mechanical properties and quantitatively analyze the polishing performances at the single contact point of a pad asperity. We first fabricate polyurethanee micro single asperitiespad asperities using…. photolithography-microreplication molding. We made hemispheric and pyramidal shaped single asperities with varying mechanical properties, and was able to attain controllability on size alsoshow…. . Then, we constructed a single-asperity CMP test system composed of a pin-on-disk tribometer integrated with a slurry injection system. Using the customized equipment we tested highly reproducible hemispheric single asperities with different hardness and characterized the polished results of SiO2 wafer surfaces. We discuss our experimental results, including the polishing width and depth, polishing rate depending on the shape, force, and mechanical properties of the pad micro asperity. We also provide theoretical model based on contact mechanics that predicts the polishing behavior and compare with the experiments. Finally, we describe how our understanding can support design and manufacturing the next-generation CMP pads and improvement of overall CMP process control.