Solving the BEOL compatibility challenge of top-pinned magnetic tunnel junction stacks

Swerts, Johan; Liu, E.; Couet, S.; Mertens, S.; Rao, Siddharth; Kim, W.; Garello, Kévin; Souriau, Laurent; Kundu, Shreya; Crotti, D.; Yasin, F.; Jossart, N.; Sakhare, Sushil; Devolder, T.; Beek, Simon Van; O’Sullivan, Barry; Elshocht, Sven Van; Furnemont, A.; Kar, Gouri Sankar

doi:10.1109/iedm.2017.8268518

Cited by 20 publications

(7 citation statements)

References 1 publication

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“…3b. With the assistance of SOT, Jth-STT as low as 0.94 MA•cm -2 can be achieved, which is a remarkable decrease compared to other current-induced mechanisms, 35,37,49 hence the ultralow power switching is expected. 48 Moreover, the reduction of charge current passing through the MgO barrier can benefit the lifetime of p-MTJ devices.…”

Section: Three-terminal Sot and Stt Devicesmentioning

confidence: 98%

Field-free switching of a perpendicular magnetic tunnel junction through the interplay of spin–orbit and spin-transfer torques

et al. 2018

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Magnetization switching by the interaction between spins and charges has greatly brightened the future of spintronic memories. [1][2][3][4][5][6] This has been evident in the rapid development of spin transfer torque-magnetic random-access memory (STT-MRAM) as a mainstream non-volatile memory technology, in which a spin-polarized current is injected into magnetic tunnel junctions (MTJs) for cell programming. 7-18 However, as cell areas scale down to meet density and power demands, conventional STT-MRAM suffers from serious endurance and reliability issues due to the aging of the ultrathin MgO barrier and read disturbance. The challenge of lowering STT switching current densities to further reduce power consumption is still yet to be met. [19][20][21] The discovery of spin-orbit torque (SOT) switching in heavy metal/ferromagnetic metal/oxide heterostructures by applying an in-plane charge current to three-terminal devices provides a promising alternative mechanism. 22-28 It shows the potential to enhance the endurance and reliability of MRAM, while improving speed and reducing power consumption. [29][30][31][32] Thus, considerable research has been triggered to further elucidate the mechanism of SOT switching, which is currently described as magnetic reversal via two vector components, the damping-like (DL) and field-like (FL) torques. 33,34 Since the demonstration of perpendicular-anisotropy MgO/CoFeB MTJs (p-MTJs), the switching of perpendicular magnetization by SOT has become of particular interest. [33][34][35][36][37][38] However, an external magnetic field collinear with the charge current is required to execute deterministic switching of p-MTJs. This intrinsic constraint, combined with the three-terminal device configuration, is limiting the practical application of SOT-MRAM. [26][27][28]35 Great efforts have been made to eliminate the need

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Section: Three-terminal Sot and Stt Devicesmentioning

confidence: 98%

Field-free switching of a perpendicular magnetic tunnel junction through the interplay of spin–orbit and spin-transfer torques

et al. 2018

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“…We note that this approach is not straightforward for SOT, as MgO would be inserted in between the SOT and FL layers, resulting in degradation of spin current transfer. As an alternative, the concept of a hybrid FL, i.e., a FL composed of a reading CoFeB-based layer coupled to a magnetic layer or multilayer with stronger PMA [190,191] was recently demonstrated [132,192,193]. This solution significantly improves the thermal stability factor to Δ > 100 in 50 nm pillars [Fig.…”

Section: Free Layermentioning

confidence: 99%

“…In fact, the atomic intermixing at interfaces and strain induced by the growth of differently textured materials lead to an overall device performance deterioration, for example, FL and SAF loss of PMA (and Ms). Whereas in-plane MTJs were readily BEOL-compatible owing to the thicker FM layer, perpendicularly magnetized MTJ stacks reached 400 °C compatibility only two years ago [190,227], and SOT-MTJ stacks were recently demonstrated [132,154]. A challenge that can significantly impact the yield is that the etching of the MTJ has to stop on the thin SOT channel precisely (typically less than 5 nm thick) without degrading its conductivity or causing vertical shorts due to metal re-deposition on the tunnel barrier sidewalls.…”

Section: Sot-mtj Integration and Challengesmentioning

confidence: 99%

Spin-orbit torque switching of magnetic tunnel junctions for memory applications

Křižáková

Perumkunnil

Couet

et al. 2022

Journal of Magnetism and Magnetic Materials

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“…In order to integrate STT-MRAM with the CMOS fabrication process, MTJs must sustain at least 400C temperature typical for the back-end-of-line process. Recently, IMEC reported a process allowing to preserve the high TMR and thermal stability of MTJs [43]. The idea is to invert the free and the fixed layer by putting the fixed layer on top of the MTJ.…”

Section: Spin-transfer Torque Mrammentioning

confidence: 99%

Demands for spin-based nonvolatility in emerging digital logic and memory devices for low power computing

Sverdlov

Selberherr²

2018

FACTA U EE

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Miniaturization of semiconductor devices is the main driving force to achieve an outstanding performance of modern integrated circuits. As the industry is focusing on the development of the 3nm technology node, it is apparent that transistor scaling shows signs of saturation. At the same time, the critically high power consumption becomes incompatible with the global demands of sustaining and accelerating the vital industrial growth, prompting an introduction of new solutions for energy efficient computations. Probably the only radically new option to reduce power consumption in novel integrated circuits is to introduce nonvolatility. The data retention without power sources eliminates the leakages and refresh cycles. As the necessity to waste time on initializing the data in temporarily unused parts of the circuit is not needed, nonvolatility also supports an instanton computing paradigm. The electron spin adds additional functionality to digital switches based on field effect transistors. SpinFETs and SpinMOSFETs are promising devices, with the nonvolatility introduced through relative magnetization orientation between the ferromagnetic source and drain. A successful demonstration of such devices requires resolving several fundamental problems including spin injection from metal ferromagnets to a semiconductor, spin propagation and relaxation, as well as spin manipulation by the gate voltage. However, increasing the spin injection efficiency to boost the magnetoresistance ratio as well as an efficient spin control represent the challenges to be resolved before these devices appear on the market. Magnetic tunnel junctions with large magnetoresistance ratio are perfectly suited as key elements of nonvolatile CMOS-compatible magnetoresistive embedded memory. Purely electrically manipulated spin-transfer torque and spin-orbit torque magnetoresistive memories are superior compared to flash and will potentially compete with DRAM and SRAM. All major foundries announced a near-future production of such memories. Two-terminal magnetic tunnel junctions possess a simple structure, long retention time, high endurance, fast operation speed, and they yield a high integration density. Combining

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Solving the BEOL compatibility challenge of top-pinned magnetic tunnel junction stacks

Cited by 20 publications

References 1 publication

Field-free switching of a perpendicular magnetic tunnel junction through the interplay of spin–orbit and spin-transfer torques

Field-free switching of a perpendicular magnetic tunnel junction through the interplay of spin–orbit and spin-transfer torques

Spin-orbit torque switching of magnetic tunnel junctions for memory applications

Demands for spin-based nonvolatility in emerging digital logic and memory devices for low power computing

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