Chemical and Biomolecular Engineering Seminar: Van-Tuan Nguyen

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Clarkson University Department of Chemical and Biomolecular Engineering Seminar Systematic Root Cause Analysis of Ceria-Induced Defects during Chemical Mechanical Planarization and Cleaning Van-Tuan Nguyen Abstract Shallow Trench Isolation Chemical Mechanical Polishing (STI-CMP) is a critical step in semiconductor manufacturing, used to planarize the wafer surface and achieve precise isolation structures between transistors. In STI-CMP, silicon dioxide material is removed from the wafer surface through a combination of mechanical friction and chemical reactions, with ceria abrasive particles suspended in a slurry. However, many defects can occur after polishing, primarily due to ceria, which adversely impacts the functionality of integrated circuit devices. Currently, ceria particles remaining on the SiO2 film after polishing from the slurry are considered the main source of ceria defects, which are then removed by the cleaning process. As semiconductor devices become smaller, ultra-smooth and defect-free surfaces become more crucial. The manufacturing of advanced devices requires strict conditions to avoid ceria defects. To meet these stringent requirements, it is important to recognize ceria-induced defects during CMP and cleaning. Our quantitative analysis of the ceria defects revealed a significant gap between the total ceria particles identified by Atomic Force Microscope (AFM) topography and the number determined by total cerium ion from Atomic Analysis (Inductively Coupled Plasma Mass Spectrometry). We hypothesized the possibilities of other ceria-induced defects during CMP and cleaning that are beyond the detection capabilities of topography analysis, including ceria remnants, small fragments, and cerium-modified layers. To determine the presence of these defects, we used AFM phase images and Scanning Electron Microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX) in addition to the AFM topography. Using AFM phase images, we found no traces of ceria remnants in the bonding parts from the embedded ceria, suggesting they might have been eliminated during the cleaning process. However, small ceria particle fragments were detected on the SiO2 films. These fragments, likely created during polishing, adhere strongly to the SiO2 film surface, resisting removal by brush scrubbing. We were also able to confirm the presence of a cerium-modified layer on the SiO2 surface, formed by the chemical interaction between ceria particles and SiO2 films during polishing. The mapping showed cerium atoms in areas without visible ceria particles. The insights from this study provide a deeper understanding of ceria-related defects in the semiconductor manufacturing process, offering valuable information for improving residue removal and surface cleaning in post-CMP processes. Wednesday, 02/21/2024 at 2:30 pm CAMP 194 Van-Tuan Nguyen is currently a Ph.D. student in the Seo Lab at Clarkson University. He graduated from Vietnam National University and Chungnam National University with his B.E. and M.E. in Chemical Engineering in 2019 and 2022, respectively. His research areas focus on the post-CMP cleaning process and Scanning Probe Microscopy.

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