Magnetic Shielding in Multilayer Memory Structures
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Solution Overview
Problem
Magnetic multilayer structures, such as magnetic tunnel junctions (MTJs) and spin valves, are susceptible to external magnetic fields, which can alter the magnetization direction of the free layer and affect the switching operation based on the spin-transfer torque effect, leading to potential interference and reduced areal density in memory devices.
Innovation Solution
Incorporating a magnetic shielding layer with a positive or negative susceptibility to shield the magnetic cell from external magnetic fields, allowing for closer packing of magnetic elements and reducing magnetic interference, thereby enhancing the areal density of memory arrays by isolating the magnetic elements from external and adjacent magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If magnetic multilayer structures are used without shielding, then device complexity is reduced, but susceptibility to external magnetic fields increases
Solution Approach 1:
A magnetic shielding layer is introduced as an intermediary component between external magnetic fields and the magnetic multilayer structure. This shielding layer, positioned adjacent to the magnetic tunnel junction or spin valve, acts as a mediator that deflects or absorbs external magnetic field lines, preventing them from directly affecting the free layer magnetization and thus reducing susceptibility while maintaining operational simplicity
Solution Approach 2:
The magnetic shielding layer is constructed using composite material structures, such as CoFeB/CoFe or CoFe/CoFeB multilayer combinations, which provide enhanced magnetic shielding effectiveness through the synergistic properties of different ferromagnetic materials. This composite approach achieves superior shielding performance compared to single-material layers, addressing the susceptibility issue while managing structural complexity
2Object-affected harmful factors
If magnetic shielding layer is added, then magnetic interference is reduced, but device complexity increases
Solution Approach 1:
The magnetic shielding layer is designed to perform multiple functions simultaneously: it provides magnetic field shielding, serves as part of the magnetic circuit, and can be integrated with existing device layers. This multi-functionality reduces the need for additional separate shielding components, thereby limiting the increase in device complexity while achieving magnetic interference reduction
Solution Approach 2:
The shielding effectiveness is optimized by adjusting parameters such as the thickness, composition, and magnetic properties of the shielding layer. By carefully controlling these parameters, adequate magnetic interference protection is achieved with minimal additional structural complexity, balancing performance improvement with device simplicity
3Ease of operation
If external magnetic fields are used for switching, then switching mechanism is simplified, but power efficiency decreases
Solution Approach 1:
The patent replaces the external magnetic field switching mechanism (which requires complex write lines and generates significant magnetic interference) with a spin-transfer torque mechanism. This substitution uses spin-polarized current flowing through the magnetic tunnel junction to directly switch the free layer magnetization, eliminating the need for external magnetic fields and reducing power consumption while simplifying the overall device structure
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 magnetic shielding effectively reduces the impact of external magnetic fields on the switching operation, enabling higher areal density memory arrays and improved power efficiency by eliminating the need for external magnetic fields for switching, thus enhancing the performance and density of magnetic memory devices.
Implementation Method 1
a magnetic shielding layer to overlay the magnetic cell on one side of the magnetic cell and operable to magnetically shield the magnetic cell from an external magnetic field
Implementation Method 2
a first ferromagnetic layer exhibiting a first magnetization that is switchable between a first direction and a second substantially opposite direction under a spin-transfer torque effect caused by an electric current
Implementation Method 3
When the thickness of the insulator layer 130 is sufficiently thin, e.g., a few nanometers or less, electrons in the two ferromagnetic layers 111 and 113 can 'penetrate' through the thin layer of the insulator due to a tunneling effect under a bias voltage applied to the two ferromagnetic layers 111 and 112 across the barrier layer 130
Implementation Method 4
The magnetic shielding layer is electrically conductive and comprising a magnetic material that exhibits a positive susceptibility under the external magnetic field
Data Source
AI summary
Techniques and device designs associated with devices having magnetically shielded magnetic or magnetoresistive tunnel junctions (MTJs) and spin valves that are configured to operate based on spin-transfer torque switching.