Quantitative Analysis of the Crystallinity of CoFeB Layers in Magnetic Random-Access Memory (MRAM) Stacks Using Extended X-ray Absorption Fine Structure Spectroscopy

Published

September 3, 2025

Author(s)

Bruce Ravel, Matthias Gottwald, Christian Lavoie, Jean Jordan-Sweet, Steve Brown, Guohan Hu

Abstract

Using Extended X-ray Absorption Fine Structure spectroscopy (EXAFS), we demonstrate a quantitative method to evaluate the degree of crystallization of thin CoFeB-based structures used in Spin Transfer Torque Magnetic Random-Access Memory (STT-MRAM). This method allows us to access a large-area-scale ( 1 cm2) for characterization of the relative degree of crystallization of ultrathin CoFeB (2 nm) when the composition and thickness of surrounding materials are varied. The presented EXAFS-based analysis method was applied to multiple combinations of metal- and oxide-capped CoFeB layer structures grown onto an MgO layer. We show how specific combinations of free layer capping and top electrode metals can significantly enhance or lower the relative degree of crystallization of a thin CoFeB layer. The impact of the capping metal layer thickness, and the effect of oxide-based capping layers (metal oxides and MgO) are also presented. Among the chemical elements tested in the current work, we find zirconium to be the most efficient in enhancing the crystallization of a 2nm thick CoFeB layer. We also find that the ability to enhance crystallization is not dramatically reduced when using metal oxides rather than pure metal capping. Future STT-MRAM stack optimization can be guided by this comprehensive study and by additional measurements using the proposed quantitative method of assessment.

Citation

Journal of Vacuum Science & Technology A

Pub Type

Journals

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https://doi.org/10.1116/6.0004422

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Keywords

MRAM, X-ray Absorption Spectroscopy

Citation

Ravel, B. , Gottwald, M. , Lavoie, C. , Jordan-Sweet, J. , Brown, S. and Hu, G. (2025), Quantitative Analysis of the Crystallinity of CoFeB Layers in Magnetic Random-Access Memory (MRAM) Stacks Using Extended X-ray Absorption Fine Structure Spectroscopy, Journal of Vacuum Science & Technology A, [online], https://doi.org/10.1116/6.0004422, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958890 (Accessed September 28, 2025)