Investigation of Mechanical Integrity and its effect on Polishing for Novel Polyurethane Polishing Pad
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Investigation of Mechanical Integrity and its effect on Polishing for Novel Polyurethane Polishing Pad Parshuram Zantye a,c, S. Mudhivarthi a,c , A. K. Sikder c, Ashok Kumar a,c , S. Ostapenko b, c and Julie Harmon d a
Department of Mechanical Engineering Department of Electrical Engineering c Nanomaterials and Nanomanufacturing Research Center, d Department of Chemistry University of South Florida, Tampa, Florida-33620 b
Abstract There is a widespread interest in development and characterization of CMP consumables due to an existing and potential market, as the CMP process becomes widely accepted in the field of microelectronics fabrication. A non-destructive Ultra Sound Testing (UST) technique developed at the University of South Florida has been successfully used in the past to map the variation of specific gravity over the entire volume of the pad. To gage the impact of the variation in specific gravity with in the body of the polishing pad, the results of UST of pads need to be correlated with actual polishing performance of the pad. In this research, UST was performed on IC 1000 Suba IV/ A4 polishing pad, and novel polyurethane pads, Pad A (with sub pad) and Pad B (without sub pad). The novel pads have been specifically developed for Interlayer Dielectric (ILD) polishing. 6 inch coupons from polishing pad regions of interest (high and low ultra sound transmission) determined after the ultrasound map were punched out and further evaluated. The mechanical properties of the pad material from the coupons were evaluated using Dynamic Mechanical Analysis (DMA) and tribological properties were evaluated by performing CMP on 6 inch coupons in the CETR CMP tester. Introduction There is a growing demand for CMP know-how, process equipment, consumables and peripherals. One such CMP consumable, where there is extensive scope for development and improvement is CMP polishing pad. The polishing pad needs to meet the ever-increasing process reproducibility and reliability demands of the semiconductor industry. The polishing pad is made up of a matrix of cast polyurethane foam with filler material to control hardness or polyurethane impregnated felts. The pad carries the slurry on top of it, executes the polishing action, and transmits the normal and shear forces for polishing (Fig. 1a) [1-5]. A stacked pad consisting of an IC1000 top layer on a Suba IV sub pad (Rodel, Inc. Newark, DE) is currently the pad system of choice to obtain both good global wafer uniformity and small step heights. The pad might be directly responsible for several process defects like wafer to wafer non uniformity (WTWNU) or within wafer non uniformity (WIWNU). In order to improve the yield of the CMP process, to get a highly planar defect free uniform wafer surface and to reduce the overall manufacturing costs involved, there is a need to extensively study the fundamental properties of the CMP pads and the materials involved there in. Dependency of the pad material properties on the CMP process has been previously studied. The drop in materi
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