Orthogonal Anisotropy MRAM Cell for Low Power TAS Writing
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Solution Overview
Problem
Conventional MRAM cells face challenges in simultaneously achieving low power consumption and thermal and temporal stability during writing operations, with thermally assisted switching (TAS) cells experiencing increased power consumption as cell size decreases, leading to high field currents and power consumption issues.
Innovation Solution
A magnetic random access memory (MRAM) cell with a thermally assisted switching (TAS) writing procedure, featuring a ferromagnetic storage layer with adjustable magnetization at a high temperature threshold, a ferromagnetic reference layer with a fixed magnetization, and an insulating layer, where the magnetocrystalline anisotropy of the storage layer is orthogonal to the reference layer, allowing for reduced magnetic field requirements and lower power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If thermally assisted switching (TAS) is used to improve thermal stability, then thermal stability is improved, but power consumption increases due to high field currents required as cell size decreases
Solution Approach 1:
The patent changes the magnetocrystalline anisotropy orientation from parallel to orthogonal between storage and reference layers, fundamentally altering the magnetic switching parameters. This enables switching at lower magnetic fields while maintaining thermal stability through the orthogonal anisotropy configuration that creates more favorable energy barriers.
Solution Approach 2:
The patent employs composite magnetic layer structures with specific material compositions (CoFeB, CoFe, MgO) that exhibit orthogonal magnetocrystalline anisotropy. The composite structure of storage layer, reference layer, and insulating layer creates the desired magnetic properties with reduced switching field requirements.
2Area of stationary object
If cell size is reduced to increase integration density, then integration density is improved, but field current and power consumption increase
Solution Approach 1:
By changing the magnetocrystalline anisotropy orientation to orthogonal, the patent modifies the magnetic switching parameters such that smaller cell sizes no longer require proportionally higher field currents. The orthogonal configuration provides more favorable switching characteristics that scale better with reduced dimensions.
Solution Approach 2:
The patent introduces a new dimension of control by utilizing orthogonal anisotropy orientation rather than the conventional parallel alignment. This dimensional change in the magnetic property space enables decoupling of cell size reduction from power consumption increase.
3Ease of manufacture
If conventional parallel magnetocrystalline anisotropy is used, then fabrication is simpler, but magnetic field requirements are higher leading to increased power consumption
Solution Approach 1:
The patent uses composite material structures (CoFeB/CoFe/MgO) that can be deposited using standard sputtering techniques while achieving orthogonal anisotropy. The composite nature allows control of magnetic properties through layer thickness and composition ratios rather than requiring complex fabrication processes.
Solution Approach 2:
The patent changes the anisotropy orientation parameter from parallel to orthogonal, which modifies the magnetic field requirements. This parameter change is achieved through controlled deposition conditions and material composition rather than fundamental fabrication process changes.
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
The solution enables writing with a magnetic field up to two times smaller than conventional TAS-MRAM cells, reducing power consumption and minimizing electromigration risks, while maintaining thermal and temporal stability, and allowing for higher integration density without compromising stability.
Implementation Method 1
passing a heating current through the magnetic tunnel junction to heat the magnetic tunnel junction to a high temperature threshold
Implementation Method 2
passing a magnetic field to align a magnetization of the ferromagnetic storage layer in a direction essentially parallel or antiparallel to a fixed magnetization of the ferromagnetic reference layer
Implementation Method 3
magnetic tunnel junctions having a strong magnetoresistance at ambient temperature
Data Source
AI summary
A magnetic random access memory (MRAM) cell with a thermally assisted switching (TAS) writing procedure, comprising a magnetic tunnel junction formed from a ferromagnetic storage layer having a first magnetization adjustable at a high temperature threshold, a ferromagnetic reference layer having a fixed second magnetization direction, and an insulating layer, said insulating layer being disposed between the ferromagnetic storage and reference layers; a select transistor being electrically connected to said magnetic tunnel junction and controllable via a word line; a current line electrically connected to said magnetic tunnel junction; characterized in that the magnetocrystalline anisotropy of the ferromagnetic storage layer is essentially orthogonal with the magnetocrystalline anisotropy of the ferromagnetic reference layer. The TAS-MRAM cell of the invention can be written with a smaller magnetic field than the one used in conventional TAS-MRAM cells and has low power consumption.