Composite Free Layer for MRAM Write Current Reduction
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Solution Overview
Problem
Magnetoresistive random access memory (MRAM) technologies face challenges in reducing write currents and power consumption while maintaining suitable tunnel magnetoresistance ratios, particularly due to high switching current densities associated with spin Hall effect-based writing, which can lead to heating and design issues.
Innovation Solution
The implementation of a composite free layer in magnetic tunnel junctions, comprising an in-plane anisotropy free layer, a ferromagnetic amorphous layer, and a perpendicular magnetic anisotropy inducing layer, along with a spin Hall effect layer, reduces switching current densities by decreasing the effective magnetization and damping constant, thereby minimizing the impact on data retention and read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spin Hall effect layer is used for writing data in SOT-MRAM, then data retention and reliability are improved, but write current density increases leading to heating and power consumption issues
Solution Approach 1:
The free layer is segmented into multiple sublayers with different magnetic anisotropy orientations. The first free layer sublayer has in-plane magnetic anisotropy while the second free layer sublayer has perpendicular magnetic anisotropy. This segmentation allows the use of spin Hall effect for reliable writing in the second sublayer while the first sublayer provides protective functionality against oxidation and interdiffusion, thus maintaining reliability without excessive current density.
Solution Approach 2:
The patent employs a composite free layer structure combining materials with different magnetic properties. The first free layer sublayer uses materials like cobalt铁硼 (CoFeB) with in-plane anisotropy, while the second sublayer uses materials with perpendicular anisotropy. This composite structure leverages the advantages of each material type to achieve both low write current density and high data retention through the spin Hall effect mechanism.
2Ease of operation
If spin-polarized current is passed through MTJ for writing data, then data can be stored, but barrier layer wear accelerates and read currents may disturb stored data
Solution Approach 1:
The patent extracts the writing function from the direct current path through the barrier layer. By implementing spin-orbit torque writing where current flows through the spin Hall effect layer adjacent to the free layer rather than through the barrier layer, the barrier layer is protected from high current stress and accelerated wear, thus improving its durability while maintaining data writing capability.
3Productivity
If high electrical currents are used for generating spin current in SOT-MRAM, then magnetic moment switching is achieved, but heating and power consumption increase
Solution Approach 1:
The patent applies local quality by creating a protective first free layer sublayer with specific material composition and magnetic anisotropy properties at the interface with the barrier layer. This sublayer has optimized local characteristics that reduce the overall current density required for switching, thereby reducing heating effects while maintaining effective magnetic moment switching in the second sublayer.
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
This configuration decreases write current densities and power consumption while maintaining a suitable tunnel magnetoresistance ratio, enhancing data retention and read operations in MRAM systems.
Implementation Method 1
an SHE layer may be configured such that an in-plane electric current within the SHE layer exerts a torque onto a composite free layer causing a spin current in the composite free layer
Implementation Method 2
A thin dielectric or barrier layer may separate the fixed and free layers, and current may flow across the barrier layer due to quantum tunneling
Implementation Method 3
a composite free layer includes an in-plane anisotropy free layer, and a ferromagnetic amorphous layer
Data Source
AI summary
Apparatuses, systems, and methods are disclosed for magnetoresistive random access memory. A magnetic tunnel junction for storing data includes a fixed layer, a barrier layer, and a composite free layer. A barrier layer is disposed between a fixed layer and a composite free layer. A composite free layer includes a ferromagnetic amorphous layer and an in-plane anisotropy free layer. A spin Hall effect (SHE) layer may be coupled to the composite free layer of the magnetic tunnel junction. The SHE layer may be configured such that an in-plane electric current within the SHE layer causes a spin current in the composite free layer.