Magnetoresistive Memory Device with Segmented Storage Layer
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Solution Overview
Problem
Current magnetoresistive random access memory (MRAM) technologies face challenges in achieving high thermal stability and reducing write current while maintaining magnetic anisotropy and thermal resistance, particularly in large-capacity MRAM devices using magnetic tunnel junction (MTJ) elements.
Innovation Solution
The use of a three-layer structure for the storage layer, where Mo is incorporated as a middle layer between magnetic material layers, and an oxide such as MgO is used as both the underlayer and tunnel barrier, enhances magnetic anisotropy and thermal resistance, reducing write current and improving thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MTJ element structure is used, then device simplicity is maintained, but thermal stability and magnetic anisotropy are insufficient
Solution Approach 1:
The storage layer is segmented into three distinct magnetic layers (first magnetic layer, second magnetic layer, third magnetic layer) with different magnetization directions and properties. This segmentation allows each layer to contribute specifically to thermal stability and magnetic anisotropy, resolving the contradiction between reliability improvement and device complexity by creating a functionally optimized multi-layer structure
Solution Approach 2:
The patent employs composite material structure where CoFeB (cobalt ferrite boride) and CoFe (cobalt ferrite) layers are combined in a specific stacking configuration. This composite approach leverages the high spin polarization of CoFeB and the strong magnetic anisotropy of CoFe to achieve enhanced thermal stability while maintaining controllable magnetization switching
2Use of energy by moving object
If write current is reduced, then energy consumption decreases, but magnetic anisotropy and thermal resistance deteriorate
Solution Approach 1:
Different magnetic layers are assigned different local qualities: the first magnetic layer has perpendicular magnetization for high thermal stability, the second magnetic layer has in-plane magnetization for easy switching, and the third magnetic layer provides additional perpendicular anisotropy. This local differentiation allows the system to achieve low write current in the easy-switching layer while maintaining high magnetic anisotropy and thermal stability through the perpendicular magnetization layers
Solution Approach 2:
The patent utilizes parameter changes in magnetization direction (from perpendicular to in-plane and vice versa) across different layers to decouple the requirements for low write current and high magnetic anisotropy. By changing the magnetization orientation parameter in specific layers, the system achieves energy-efficient switching without compromising thermal stability
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 significantly improves magnetic properties and thermal stability, allowing for efficient operation with reduced write current, especially when the middle layer is formed with Mo and the underlayer is MgO, enhancing perpendicular magnetic anisotropy and thermal resistance.
Implementation Method 1
magnetoresistive random access memory (MRAM) in which a magnetic tunnel junction (MTJ) element is used
Implementation Method 2
one of the two magnetic layers which sandwich a tunnel barrier layer is formed as a magnetization fixed layer (a reference layer) in which the direction of magnetization is fixed to be invariable
Data Source
AI summary
A magnetoresistive memory device includes a first magnetic layer having a variable magnetization direction, a second magnetic layer, a magnetization direction of the second magnetic layer being invariable, a first nonmagnetic layer provided between the first magnetic layer and the second magnetic layer, and a second nonmagnetic layer provided on the first magnetic layer, which is opposite the first nonmagnetic layer. The first magnetic layer has a stacked layer structure in which an amorphous magnetic material layer is sandwiched between crystalline magnetic material layers. The magnetoresistive memory device further includes nonmagnetic material layers provided between one of the crystalline magnetic material layers and the amorphous magnetic material layer, and between the other crystalline magnetic layer and the amorphous magnetic material layer, respectively.