(Invited) Towards Metrology to Enable Standardizing CMP Consumables

In the semiconductor industry, there is a need to establish fundamental, mechanism-based, correlation(s) between process conditions, consumables (e.g., pads and slurries), and observed process performance in Chemical-Mechanical Polishing (CMP) [1-5]. Such understanding can lead to the creation of industry-wide standards that can help reduced cost of ownership. Along these lines, the Chemical Mechanical Planarization Consumables (CMP-C) Task Force under Liquid Chemicals Global Technical Committee within the SEMI Standards Program has been actively developing a guide (SEMI C100) for reporting CMP pad hardness [6], and pad density. In this paper, we revisit our decades old, but still relevant, quest for suitable mechanism-based metrology for CMP-pad. While we focus on polyurethane-based CMP pads, we will touch on alternative pad materials. [10-11]. Using both static and dynamic the dynamic mechanical analysis (DMA) [7-8] and the FTIR [9] we monitored changes in pad polymer properties under various chemical and mechanical stresses. Pad sample were analyzed: prior to use (fresh); after a 24-hr soak in silica-containing oxide slurry (basic); and after oxide polishing (used). Upon comparison it was observed that a characteristic transition feature due to water is present at sub-ambient temperatures in both the slurry soaked and used pads. Exposure of as-received pads to basic oxide slurry results in a broad, high temperature transition thought to be the result of chemical-induced disruption of macrostructural units. Polishing (load-enhanced chemical exposure) introduces further changes to the polymer network represented by an apparent degradation of the pad polymer. References 1) P. B. Zantye, et al, 'Chemical mechanical planarization for microelectronics applications, Materials Science and Engineering: R: Reports, 2004, 45, 3–6, doi: 10.1016/j.mser.2004.06.002. 2) Zantye, Parshuram B., "Processing, Reliability and Integration Issues In Chemical Mechanical Planarization" (2005). Graduate Theses and Dissertations, https://scholarcommons.usf.edu/etd/928 3) S. Deshpande et al, “The Electrochemical Society, find out more Chemical Mechanical Planarization of Copper: Role of Oxidants and Inhibitors”, 2004 J. Electrochem. Soc. 151 G788 4) Y. S. Obeng et al., "Impact of CMP consumables on copper metallization reliability," in IEEE Transactions on Semiconductor Manufacturing, vol. 18, no. 4, pp. 688-694, Nov. 2005, doi: 10.1109/TSM.2005.858457. 5) Obeng, Yaw S., et al. "Characterization of ‘In-Process’ Degradation of Polyurethane CMP Pads." Chemical Mechanical Planarization V 2002 (2002): 1. 6) SEMI C100 - Guide for Reporting Chemical Mechanical Planarization (CMP) Polishing Pads Hardness Used, published by SEMI Standards (https://store-us.semi.org/products/c10000-semi-c100-guide-for-reporting-chemical-mechanical-planarization-cmp-polishing-pads-hardness-used-in-semiconductor-manufacturing, accessed December 15, 2020) 7) Li et al, “Dynamic Mechanical Analysis (DMA) of CMP pad materials”, MRS Proceedings, January 2000, Cambridge University Press, DOI: 10.1557/proc-613-e7.3.1 8) H. Lu et al, "Applicability of dynamic mechanical analysis for CMP polyurethane pad studies” Materials Characterization, 2002, 49, 2, 177-186, DOI: 10.1016/S1044-5803(03)00004-4. 9) H Lu, et al., "Quantitative analysis of physical and chemical changes in CMP polyurethane pad surfaces, Materials Characterization", 2002,49, 1, 35-44, DOI: 10.1016/S1044-5803(02)00285-1. 10) S. Deshpande, et al. “Surface-modified polymeric pads for enhanced performance during chemical mechanical planarization”, Thin Solid Films, 2005, 483, 1–2, 261-269, DOI: 10.1016/j.tsf.2004.12.063. 11) Zantye, P., et al., “Metrology of Psiloquest's Application Specific Pads (ASP) for CMP Applications”. MRS Proceedings, (2004). 816, K5.6. doi:10.1557/PROC-816-K5.6