Process-induced damage and its recovery for a CoFeB–MgO magnetic tunnel junction with perpendicular magnetic easy axis

Kinoshita, Keizo; Honjo, Haruo; Fukami, Shunsuke; Sato, Hideo; Mizunuma, K.; Tokutome, K.; Murahata, Michio; Ikeda, Shoji; Kasai, N.; Ohno, Hideo

doi:10.7567/jjap.53.103001

Cited by 21 publications

(12 citation statements)

References 40 publications

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“…This is likely due to patterning effects such as disorder of the local crystal structure or stoichiometry at the edges. Such effects become more pronounced as the critical dimension is reduced and the edge region makes up a larger fraction of the total volume 30,31 . Fig.…”

Section: B Size Dependence Of Recording Layer Coercivitymentioning

confidence: 99%

Size and voltage dependence of effective anisotropy in sub-100-nm perpendicular magnetic tunnel junctions

et al. 2016

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Magnetic tunnel junctions with perpendicular magnetic anisotropy are investigated using a conductive atomic force microscope. The 1.23 nm Co 40 Fe 40 B 20 recording layer coercivity exhibits a size dependence which suggests single domain behavior for diameters ≤ 100 nm. Focusing on devices with diameters smaller than 100 nm, we determine the effect of voltage and size on the effective device anisotropy K eff using two different techniques. K eff is extracted both from distributions of the switching fields of the recording and reference layers, and from measurement of thermal fluctuations of the recording layer magnetization when a field close to the switching field is applied. The results from both sets of measurements reveal that K eff increases monotonically with decreasing junction diameter, consistent with the size dependence of the demagnetization energy density. We demonstrate that K eff can be controlled with a voltage down to the smallest size measured, 64 nm. PACS numbers: 85.75.-d,73.40.Gk,75.78.-n,75.70.-i 1 I. INTRODUCTION Magnetic tunnel junctions (MTJs) with perpendicular magnetic anisotropy (PMA) are an attractive building block for non-volatile memories. PMA MTJs (p-MTJs) show promisein terms of the key requirements for implementation into products competitive with current data storage and memory technologies: large tunnel magnetoresistance (TMR), low writing energy cost, non-volatility over ∼ 10 years, and scalability of these properties toward ∼ 1 Tbit/inch 2 densities. Room temperature TMR ratios greater than 100% have long existed in in-plane MTJs 1,2 . In state of the art in-plane MTJs, TMR in excess of 600% is achieved by controlling the diffusion of Ta in the film stack through the addition of boron to the magnetic electrodes 3 . Despite these achievements, in-plane MTJs suffer from scalability issues due to their dependence on shape anisotropy for thermal stability and the high energy cost of switching the magnetization by the spin transfer torque (STT) effect 4,5 . For in-plane MTJs, switching energies E sw = I 2 c Rt, where I c is the critical switching current, R is the resistance, and t is the length of the pulse, of approximately 10 µJ/bit were achieved for current pulses on the order of 10 ms 6 . This value was drastically reduced using nanosecond pulses, yielding E sw on the order of single pJ/bit in purely in-plane MTJs 7 . In high TMR p-MTJs the large out-of-plane demagnetization energy does not contribute to E sw 8 . Recently, TMR ratios up to 162% were obtained in p-MTJs by further controlling interlayer diffusion through the substitution of Ta with Mo in the film stack 9 . PMA is achieved when the CoFeB thickness is less than about 1.5 nm, so that the effective anisotropy K eff is dominated by the interfacial anisotropy between Fe in the CoFeB and oxygen in the MgO 10 . In such p-MTJs, switching energies of hundreds of fJ/bit were achieved in 60 nm × 170 nm ellipses 11 . One of the most promising aspects of p-MTJs is that the interface anisotropy can be controlled by applying a...

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Section: B Size Dependence Of Recording Layer Coercivitymentioning

confidence: 99%

Size and voltage dependence of effective anisotropy in sub-100-nm perpendicular magnetic tunnel junctions

et al. 2016

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“…88,89) Additional methods include methanol plasma etching, which requires further improvement in maintaining the etching selectivity and pattern transfer fidelity for high aspect ratio features. [88][89][90][91] ALEt can be partly considered as the reverse of ALD, and through the utilization of chemistries inspired by ALD precursors, can be controlled by exploiting the self-limiting nature of one of the surface reactions. Table II summarizes the general characteristics of ALD and ALEt, including the advantages of using thermal and plasma-enhanced ALD= ALEt, namely, the ability to achieve anisotropy using charged species as well as precise composition control and selectivity.…”

Section: Atomic Layer Processing Of Multiferroic Materialsmentioning

confidence: 99%

Progress and prospects in nanoscale dry processes: How can we control atomic layer reactions?

Ishikawa

Karahashi

Ichikı

et al. 2017

Jpn. J. Appl. Phys.

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In this review, we discuss the progress of emerging dry processes for nanoscale fabrication. Experts in the fields of plasma processing have contributed to addressing the increasingly challenging demands in achieving atomic-level control of material selectivity and physicochemical reactions involving ion bombardment. The discussion encompasses major challenges shared across the plasma science and technology community. Focus is placed on advances in the development of fabrication technologies for emerging materials, especially metallic and intermetallic compounds and multiferroic, and two-dimensional (2D) materials, as well as state-of-the-art techniques used in nanoscale semiconductor manufacturing with a brief summary of future challenges.

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“…Practically, MTJ device property degradation (e.g., coercivity and TMR ratio decrease) induced by either method is the major issue to be overcome. Kinoshita et al [38] investigated this damage and proposed post-etching treatment using reductive He/H2 plasma, specifically for the CoFeB/MgO structure based MTJ with interfacial PMA. In this study, Methanol gas, which exhibits high etching selectivity against Ta hard mask, was used to conduct ICP processing.…”

Section: Device Etchingmentioning

confidence: 99%

Tunnel Junction with Perpendicular Magnetic Anisotropy: Status and Challenges

et al. 2015

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Magnetic tunnel junction (MTJ), which arises from emerging spintronics, has the potential to become the basic component of novel memory, logic circuits, and other applications. Particularly since the first demonstration of current induced magnetization switching in MTJ, spin transfer torque magnetic random access memory (STT-MRAM) has sparked a huge interest thanks to its non-volatility, fast access speed, and infinite endurance. However, along with the advanced nodes scaling, MTJ with in-plane magnetic anisotropy suffers from modest thermal stability, high power consumption, and manufactural challenges. To address these concerns, focus of research has converted to the preferable perpendicular magnetic anisotropy (PMA) based MTJ, whereas a number of conditions still have to be met before its practical application. This paper overviews the principles of PMA and STT, where relevant issues are preliminarily discussed. Centering on the interfacial PMA in CoFeB/MgO system, we present the fundamentals and latest progress in the engineering, material, and structural points of view. The last part illustrates potential investigations and applications with regard to MTJ with interfacial PMA.

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Process-induced damage and its recovery for a CoFeB–MgO magnetic tunnel junction with perpendicular magnetic easy axis

Cited by 21 publications

References 40 publications

Size and voltage dependence of effective anisotropy in sub-100-nm perpendicular magnetic tunnel junctions

Size and voltage dependence of effective anisotropy in sub-100-nm perpendicular magnetic tunnel junctions

Progress and prospects in nanoscale dry processes: How can we control atomic layer reactions?

Tunnel Junction with Perpendicular Magnetic Anisotropy: Status and Challenges

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