Multi-Interface Free Layer for pMTJ Spin State Stability
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Solution Overview
Problem
Magnetoresistive random-access memory (MRAM) has been sidelined due to a tradeoff between size and performance, with MRAM cells facing issues in maintaining spin states and differentiating between values of zero and one, especially at smaller sizes.
Innovation Solution
The implementation of a perpendicular magnetic tunnel junction (pMTJ) with a multi-interface free layer (MIFL) composed of various materials, such as CoFeB and MgO or Ta, to optimize characteristics like high resolution and switching speeds while maintaining a small profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If MRAM cell size is reduced, then device compactness is improved, but spin state maintenance and value differentiation become insufficient
Solution Approach 1:
The free layer is segmented into multiple sublayers (first sublayer, second sublayer, third sublayer) with different materials and magnetic properties. This segmentation allows each sublayer to contribute differently to the overall magnetic moment, enabling sufficient spin state differentiation even when the total cell size is reduced.
Solution Approach 2:
Different sublayers are assigned different local qualities - specifically, different materials with different saturation magnetizations (Ms). The first sublayer has higher Ms than the second and third sublayers, creating local magnetic moment variations that enhance spin state stability and differentiation within the compact structure.
2Area of moving object
If MRAM cell size is reduced, then device compactness is improved, but resolution between zero and one values deteriorates
Solution Approach 1:
The free layer is divided into multiple sublayers with different magnetic moments, allowing the parallel and antiparallel states to have more distinct total magnetic moments. This segmentation enhances the resolution between logic 0 and logic 1 states even in reduced-size cells.
Solution Approach 2:
The free layer uses composite material structure with at least three different materials forming sublayers. This composite approach creates distinct magnetic moment contributions from each sublayer, improving the detectability and resolution of binary states in compact MRAM cells.
3Device complexity
If single material free layer is used, then device simplicity is improved, but switching speed and resolution optimization are limited
Solution Approach 1:
The free layer employs composite materials with at least three different substances, where the first sublayer has higher saturation magnetization than the second and third sublayers. This composite structure enables optimized switching speed by creating favorable magnetic moment distributions and anisotropy, while the multi-layer design allows for tailored magnetic properties that enhance switching performance.
Solution Approach 2:
Different materials are strategically placed in different sublayers to create local magnetic property variations. The first sublayer's higher Ms compared to the other sublayers creates specific local magnetic characteristics that facilitate faster switching while maintaining overall structural organization.
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 enhances the resolution between zero and one states and improves switching speeds in MRAM cells, addressing performance issues and maintaining non-volatility, even at smaller sizes.
Implementation Method 1
A perpendicular magnetic tunnel junction (pMTJ) with a multi-interface free layer is described which is suitable for magnetoelectric devices
Implementation Method 2
Magnetoresistive random-access memory (MRAM) is an alternative memory technology to FLASH random-access memory and dynamic random-access memory (DRAM) that relies on magnetic storage elements
Data Source
AI summary
A magnetic memory cell can include a reference ferromagnetic layer; a barrier layer on the reference ferromagnetic layer; a multiple-interface free layer (MIFL) on the barrier layer; and a capping layer on the MIFL. The MIFL has at least three coupled sublayers, providing at least four interfaces for the MIFL.