A Word Line Pulse Circuit Technique for Reliable Magnetoelectric Random Access Memory

Lee, Hochul; Lee, Albert; Wang, Shaodi; Ebrahimi, Farbod; Gupta, Puneet; Amiri, Pedram Khalili; Wang, Kang L.

doi:10.1109/tvlsi.2017.2670502

Cited by 18 publications

(12 citation statements)

References 20 publications

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“…studied the effect of pulse shapes on the precessional switching process using a macro‐spin model. They proposed a word‐line pulsing method to generate better square‐shaped pulses, effectively by using the nonlinearity of the access transistor, when VCMA‐MTJs are integrated with CMOS as shown in Figure 1. [131 ] As shown in Figure a when a square‐shaped pulse is applied to the device, the PMA is eliminated abruptly, therefore the effective field becomes in‐plane abruptly as well and stays constant during the voltage pulse, which provides a stable axis for the precession of the magnetic moment.…”

Section: Challenges and Research Opportunities For Vcma‐mrammentioning

confidence: 99%

Progress and Application Perspectives of Voltage‐Controlled Magnetic Tunnel Junctions

Shao,

Khalili Amiri

2023

Adv Materials Technologies

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This article discusses the current state of development, open research opportunities, and application perspectives of electric‐field‐controlled magnetic tunnel junctions that use the voltage‐controlled magnetic anisotropy effect to control their magnetization. The integration of embedded magnetic random‐access memory (MRAM) into mainstream semiconductor foundry manufacturing opens new possibilities for the development of energy‐efficient, high‐performance, and intelligent computing systems. The current generation of MRAM, which uses the current‐controlled spin‐transfer torque (STT) effect to write information, has gained traction due to its nonvolatile data retention and lower integration cost compared to embedded Flash. However, scaling MRAM to high bit densities will likely require a transition from current‐controlled to voltage‐controlled operation. In this perspective, an overview of voltage‐controlled magnetic anisotropy (VCMA) as a promising beyond‐STT write mechanism for MRAM devices is provided and recent advancements in developing VCMA‐MRAM devices with perpendicular magnetization are highlighted. Starting from the fundamental mechanisms, the key remaining challenges of VCMA‐MRAM, such as increasing the VCMA coefficient, controlling the write error rate, and achieving field‐free VCMA switching are discussed. Then potential solutions are discussed and open research questions are highlighted. Lastly, prospective applications of voltage‐controlled magnetic tunnel junctions (VC‐MTJs) in security applications, extending beyond their traditional role as memory devices are explored.

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Section: Challenges and Research Opportunities For Vcma‐mrammentioning

confidence: 99%

Progress and Application Perspectives of Voltage‐Controlled Magnetic Tunnel Junctions

Shao,

Khalili Amiri

2023

Adv Materials Technologies

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“…The VCMA has two stable opposite states, parallel and anti-parallel, represented by m z ≈ 1 and m z ≈ −1, respectively. Although normally the write pulse is applied in the BL, the authors in [38] showed that applying the write pulse in the WL leads to a better pulse shape compared to when the write pulse is applied in the BL of the MeRAM. Moreover, it improves the switching probability and minimizes the area overhead (e.g., driver size) [38].…”

Section: Vcma-mtj Based Meram Bit-cellmentioning

confidence: 99%

“…Although normally the write pulse is applied in the BL, the authors in [38] showed that applying the write pulse in the WL leads to a better pulse shape compared to when the write pulse is applied in the BL of the MeRAM. Moreover, it improves the switching probability and minimizes the area overhead (e.g., driver size) [38]. Figure 6 gives an example of the precession of magnetization under the influence of a voltage between the MTJ's terminals.…”

Section: Vcma-mtj Based Meram Bit-cellmentioning

confidence: 99%

“…The results show that, even if it has some advantages to apply the pulse in BL [38], it is important that the other writing lines (BL and SL) are not activated much before the beginning of the WL pulse (worst Q c at 100 ps before-see Figure 12a). In addition, BL and SL should be deactivated as soon as possible, that is, not much after of the end of the WL pulse (worst Q c at just over 150 ps-see Figure 12b).…”

Section: Case 2: With Write Pulsementioning

confidence: 99%

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Voltage-Controlled Magnetic Anisotropy MeRAM Bit-Cell over Event Transient Effects

Maciel

Marques

Naviner

et al. 2019

JLPEA

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Magnetic tunnel junction (MTJ) with a voltage-controlled magnetic anisotropy (VCMA) effect has been introduced to achieve robust non-volatile writing control with an electric field or a switching voltage. However, continuous technology scaling down makes circuits more susceptible to temporary faults. The reliability of VCMA-MTJ-based magnetoelectric random access memory (MeRAM) can be impacted by environmental disturbances because a radiation strike on the access transistor could introduce write and read failures in 1T-1MTJ MeRAM bit-cells. In this work, Single-Event Transient (SET) effects on a VCMA-MTJ-based MeRAM in 28 nm FDSOI CMOS technology are investigated. Results show the minimum SET charge Q c required to reach the access transistor associated with the striking time that can lead to an unsuccessful switch, that is, an error in the writing process (write failure). The synchronism between the fluctuations of the magnetic field in the MTJ free layer and the moment of the write pulse is also analyzed in terms of SET robustness. Moreover, results show that the minimum Q c value can vary more than 100% depending on the magnetic state of the MTJ and the width of the access transistor. In addition, the most critical time against the SET occurrence may be before or after the write pulse depending on the magnetic state of the MTJ.

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“…Some studies on VCMA using the micromagnetic framework aim at explaining the magnetization reversal process under the influence of an electric field, with some design approaches being proposed 19 – 21 . A broad variety of macrospin studies exist, oriented towards the optimization of system operation through pulse shape 22 , 23 , thermal stability 24 and towards decreasing of the write-error-rate (WER), some of which accompanied by experimental studies 18 , 24 – 26 . Other macrospin studies focus on the association between VCMA and spin transfer torque (STT) methods of magnetization manipulation 27 or on the VCMA and a Rashba field which is used as an in-plane bias magnetic field 25 .…”

Section: Introductionmentioning

confidence: 99%

Route towards efficient magnetization reversal driven by voltage control of magnetic anisotropy

One

Béa

Mican

et al. 2021

Sci Rep

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The voltage controlled magnetic anisotropy (VCMA) becomes a subject of major interest for spintronics due to its promising potential outcome: fast magnetization manipulation in magnetoresistive random access memories with enhanced storage density and very low power consumption. Using a macrospin approach, we carried out a thorough analysis of the role of the VCMA on the magnetization dynamics of nanostructures with out-of-plane magnetic anisotropy. Diagrams of the magnetization switching have been computed depending on the material and experiment parameters (surface anisotropy, Gilbert damping, duration/amplitude of electric and magnetic field pulses) thus allowing predictive sets of parameters for optimum switching experiments. Two characteristic times of the trajectory of the magnetization were analyzed analytically and numerically setting a lower limit for the duration of the pulses. An interesting switching regime has been identified where the precessional reversal of magnetization does not depend on the voltage pulse duration. This represents a promising path for the magnetization control by VCMA with enhanced versatility.

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A Word Line Pulse Circuit Technique for Reliable Magnetoelectric Random Access Memory

Cited by 18 publications

References 20 publications

Progress and Application Perspectives of Voltage‐Controlled Magnetic Tunnel Junctions

Progress and Application Perspectives of Voltage‐Controlled Magnetic Tunnel Junctions

Voltage-Controlled Magnetic Anisotropy MeRAM Bit-Cell over Event Transient Effects

Route towards efficient magnetization reversal driven by voltage control of magnetic anisotropy

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