Magnetoelectric Junctions with Seed and Cap Layers for Low-Power MRAM
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Solution Overview
Problem
Conventional magnetoresistive random-access memory (MRAM) technologies face challenges such as high power consumption and large switching currents, especially when bit size shrinks below 100 nm, and require improvements in switching current density and writability.
Innovation Solution
The implementation of robust magnetoelectric junctions (MEJs) with specific configurations, including ferromagnetic fixed and free layers, dielectric layers, and seed/cap layers made of materials like Molybdenum, Tungsten, Iridium, Bismuth, Rhenium, and Gold, which demonstrate stronger perpendicular magnetic anisotropy, tunnel magnetoresistance, and voltage-controlled magnetic anisotropy, reducing coercivity and enhancing writability and readability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional MRAM technologies use Oersted field or spin transfer torque to write magnetization, then magnetization switching can be achieved, but large current and high power consumption are required
Solution Approach 1:
The patent changes the physical parameter of magnetic anisotropy from in-plane to perpendicular by introducing specific seed and cap layers (Molybdenum, Tungsten, Iridium, Bismuth, Rhenium, or Gold). This parameter change enables voltage-controlled magnetic anisotropy (VCMA) effect, allowing magnetization switching at much lower power consumption while maintaining switching capability through electric field control of the perpendicular magnetic anisotropy energy barrier
Solution Approach 2:
The patent replaces the conventional current-based Oersted field or spin transfer torque mechanism with an electric field-based voltage control mechanism. By applying voltage across the dielectric layer, the electric field directly modulates the perpendicular magnetic anisotropy of the ferromagnetic free layer, enabling magnetization switching without requiring large currents, thus substituting a high-power electrical mechanism with a low-power electrical mechanism
2Area of moving object
If bit size is reduced below 100 nm, then device density is improved, but switching current density increases
Solution Approach 1:
The patent changes the magnetic anisotropy parameter to perpendicular orientation through specific material layer selection (seed and cap layers), which fundamentally alters the energy landscape of the magnetic system. This enables the VCMA effect to dominate, allowing efficient magnetization switching in miniaturized bits below 100 nm without the current density penalty that would normally accompany size reduction
Solution Approach 2:
The patent employs composite material structures with specific seed and cap layers (Molybdenum, Tungsten, Iridium, Bismuth, Rhenium, or Gold) combined with ferromagnetic layers and dielectric layers. This composite structure engineering creates strong perpendicular magnetic anisotropy and enhances VCMA effect, enabling scalable miniaturization while maintaining low switching energy requirements through the synergistic interaction of different material properties
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These MEJs achieve improved writability and readability with reduced coercivity and lower current requirements, enabling more efficient and robust MRAM devices with enhanced thermal resilience and performance.
Implementation Method 1
when a potential difference is applied across the aggregate of the cap layer, the first ferromagnetic fixed layer, the dielectric layer, the ferromagnetic free layer, and the seed layer, the coercivity of the ferromagnetic free layer is reduced for the duration of the application of the potential difference
Implementation Method 2
These devices utilize quantum-mechanical magnetoresistance effects, such as giant magnetoresistance (GMR) and tunnel magnetoresistance (TMR). GMR and TMR principles regard how the resistance of a thin film structure that includes alternating layers of ferromagnetic and non-magnetic layers depends upon whether the magnetizations of ferromagnetic layers are in a parallel or antiparallel alignment
Implementation Method 3
the magnetoelectric junction is configured such that it demonstrates stronger perpendicular magnetic anisotropy
Data Source
AI summary
Robust magnetoelectric junctions (MEJs) are disclosed. In one embodiment, an MEJ includes: a first fixed layer; a free layer; a seed layer; a cap layer; and a dielectric layer disposed between the first fixed layer and the free layer; where: one of the seed layer and the cap layer is disposed adjacently to a ferromagnetic layer; the first fixed layer is magnetized in a first direction; the free layer can adopt a magnetization direction that is either substantially parallel with or substantially antiparallel with the first direction; when a potential difference is applied across the MEJ, the coercivity of the free layer is reduced for the duration of the application of the potential difference; and at least one of the seed layer and the cap layer includes one of: Molybdenum, Tungsten, Iridium, Bismuth, Rhenium, and Gold.