Development of Electrochemical Copper Deposition Screening Methodologies for Next Generation Additive Selection
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Development of Electrochemical Copper Deposition Screening Methodologies for Next Generation Additive Selection Kevin Ryan1 Kathleen Dunn1 and Jobert van Eisden2 1 College of Nanoscale Science and Engineering at SUNY Albany, 255 Fuller Rd, Albany, NY 12222, U.S.A. 2 Atotech USA, 255 Fuller Rd, Albany, NY 12222, U.S.A. ABSTRACT To reduce time-to-knowledge and costs associated with wafer scale processing a laboratory scale copper electrochemical deposition (ECD) system was developed for screening new organic additives which promote bottom-up fill in interconnect trenches and vias. This new setup enables working process conditions and functionality trends to be identified for open source and proprietary suppressors and levelers at leading edge feature sizes (sub 50nm). The laboratory results can then be compared to the in-line wafer scale plating tool results to ensure their compatibility. A reliable laboratory setup that can mimic the dynamic conditions found inside the wafer scale plating tool will enable the main objective of this work to be efficiently realized. The main objective is to test two previously published models describing copper fill inside the trenches by bridging the gap between fundamental electrochemical measurements and wafer scale plating results. To date this work will focus on the reliability and transferability of plating results between the laboratory setup and a wafer scale plating tool and present preliminary data using gap fill and bottom-up growth ratio as performance metrics. INTRODUCTION Copper electrochemical deposition inside trenches created by the dual damascene process has proven to be a robust and reliable technology for the fabrication of high end interconnect devices.1-4 To achieve void free copper fill inside these ever shrinking structures organic additives must be incorporated into the base electrolyte. These additives have unique properties that allow them to suppress copper growth on the non-patterned field and trench sidewalls while accelerating the growth from the bottom of the trench (bottom-up fill). Without these additives a conformal fill will result leading to copper build up at the via opening which leaves an unacceptable void.3 The development of these additive packages is a highly competitive market which requires companies to keep the chemical formula of their proprietary additives a trade secret. However, a set of open chemistry additives exists to allow for academic research and comparing results between different research groups. In addition to these organic molecules, addition of Cl- ions to the electrolyte is necessary to facilitate suppressor adsorption onto the copper surface.5 Several groups have proposed different mechanisms to explain the interaction of additives inside the trench and their effect on the copper deposit.3,6-15 The two models that stand out in the literature are the adsorption-diffusion model proposed by A. C. West6 and the Curvature Enhanced Accelerator Coverage (CEAC) model proposed by Josell et. al.7 These models offer a method to extra
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