Study of Slurry Composition Transition in a Rotary Copper CMP Process
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Study of slurry composition transition in a rotary Copper CMP process Sharath Hegde, Udaya B. Patri, Anurag Jindal* and S.V. Babu Department of Chemical Engineering, Center for Advanced Materials Processing, Clarkson University, Potsdam, NY 13699 Abstract The polishing pad is one of the prime components in a typical Chemical Mechanical Polishing (CMP) process. The structure and transport properties of a polishing pad are critical in determining the particle and chemical utilization in a conventional CMP process. Our earlier paper investigated the particle retention and transport on two different polishing pads, IC-1400 and Suba-500, during copper polishing. In this paper, the results of chemical retention and transport of IC-1400 and Suba-500 pads during copper polishing are presented. The polish rate results from slurry-step-flow experiments with H2O2-glycine based slurries, where the concentrations of chemicals in the slurry are altered in steps during polishing, are correlated to the chemical retention and transport characteristics of these pads. It is found that IC-1400 has a higher chemical transport capability than Suba-500 pad, which is shown to affect the polish rates of copper. Introduction Chemical Mechanical Planarization (CMP) is widely recognized as the planarization technique of choice in ultra large-scale integration technology (ULSI) for integrated circuit fabrication [1, 2]. One of the prime components of a typical CMP process is the polishing pad. CMP slurry components including abrasive particles and chemicals are continuously introduced onto the pad during polishing and an efficient transport of these abrasives and chemicals across the wafer is required to achieve removal rate uniformity in all regions of the wafer. The ability to retain or release the slurry components in a typical polishing process is greatly determined by the microstructure of the pad. Although modeling of slurry flow beneath the wafer has been reported earlier [3-5], chemical retention and transport capability of the polishing pad has received little attention [6]. The retention of abrasives in a slurry containing silica, hydrogen peroxide (H2O2) and glycine on two kinds of conventional pads, IC-1400 and Suba-500 was investigated in our earlier paper [7]. This paper, in continuing that previous work, investigates the transport of the chemicals, hydrogen peroxide and glycine on these two pads. Experimental CMP of 6 inch blanket copper films and 32 mm copper disks (99% pure) was performed on a Westech-372 polisher and a Struers® bench top polisher, respectively. Copper disks were polished on IC-400 k-groove and Suba-500 pads at 6.3 psi down force at a relative linear velocity of ~50 cm/sec and 60 ml/min slurry flow while copper films were polished on an IC1400 k-grooved pad at 6.0 psi down-force, a relative linear velocity of ~ 50 cm/sec and slurry flow rate of 60 ml/min. The pad was hand conditioned for one minute before every experiment. Polish rate of the disk was obtained from its weight loss while that of the blank
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