Abstract
With scaling beyond 40um pitch 3D interconnects, cost, performance and reliability become ever more critical. Thiol-based self-assembled monolayers (SAM) were applied before to enable Cu-Cu connection in dual damascene vias [1]. In this study, we are researched a parallel application, for an alternative, low-cost organic surface finish for electroplated Cu pads/pillar/bumps to enable 3D interconnects [2]. The effects of pre-cleaning, deposition times and self-assembled monolayer (SAM) type (C3, C10, C18) on oxidation resistance and electrical continuity were studied with Voltammetry and X-ray Photoelectron Spectroscopy (XPS). Experiments were performed on electroplated Cu flat samples and process conditions were selected for further processing of 3D patterned dies and subsequent stacking and thermo-compression bonding in a face-to-face configuration. Overall, C18 SAM showed better electrical continuity and lower electrical resistance than C3 and C10, a result which is consistent with the longer C chain and higher thermal stability of C18. A second result of this study — consistent in both flat and patterned samples — was that microwave plasma cleaning prior to SAM deposition was more effective than wet cleaning, indicating either better oxide cleanability or better affinity of SAM’s with more pristine Cu.
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References
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© 2015 TMS (The Minerals, Metals & Materials Society)
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Armini, S. et al. (2015). Thiol-Based Self-Assembled Monolayers (SAMs) as an Alternative Surface Finish for 3D Cu Microbumps. In: TMS 2015 144th Annual Meeting & Exhibition. Springer, Cham. https://doi.org/10.1007/978-3-319-48127-2_161
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DOI: https://doi.org/10.1007/978-3-319-48127-2_161
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-48608-6
Online ISBN: 978-3-319-48127-2
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