Perpendicular Magnetic Anisotropy Memory Reducing Write Current
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Solution Overview
Problem
Current magnetic memory technologies face challenges in reducing write current while maintaining thermal stability and scalability, particularly with the spin torque transfer and current driven domain wall motion methods, which require high current densities and can lead to increased chip area and power consumption.
Innovation Solution
A magnetic memory with a data storage layer made of ferromagnetic material having perpendicular magnetic anisotropy, utilizing a laminated structure with underlayers to achieve controlled domain wall motion, reducing write current by optimizing material properties and crystal orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a magnetic field is generated by flowing write current through an interconnection to switch magnetization direction, then high speed operation (one nanosecond or less) is achieved, but write current increases to several mA and chip area increases
Solution Approach 1:
The patent replaces the magnetic field generation method (electromagnetic induction through interconnection) with a direct spin torque transfer mechanism. By supplying write current directly between the first and second magnetic layers, the invention eliminates the need for separate write interconnections and achieves magnetization switching through spin-polarized electron transport, thereby reducing write current and chip area while maintaining high-speed operation
Solution Approach 2:
The invention extracts the write current path from the read current path by providing a dedicated write current path between the first and second magnetic layers. This separation allows the write operation to use a different current route than the read operation, enabling independent optimization of write current magnitude and eliminating the need for high current through the read interconnections
2Stability of the object's composition
If spin torque transfer method is used with insulating layer between magnetic layers, then magnetization reversal is achieved, but write current increases and rewriting durability decreases
Solution Approach 1:
The patent changes the magnetic anisotropy parameter from in-plane to perpendicular magnetic anisotropy in the first magnetic layer. This parameter change enables magnetization reversal at lower current densities and improves the durability of repeated write operations. The perpendicular anisotropy is achieved through specific material composition and thin film structure, fundamentally altering the energy landscape for magnetization switching
3Area of moving object
If element size is reduced for scaling, then memory density increases, but write current increases in spin torque transfer method
Solution Approach 1:
The invention changes the magnetic anisotropy parameter to perpendicular orientation, which fundamentally alters the scaling behavior. With perpendicular anisotropy, the write current decreases as element size decreases, opposite to the spin torque transfer behavior with in-plane anisotropy. This parameter change enables simultaneous achievement of high density and low power consumption
4Use of energy by moving object
If perpendicular magnetic anisotropy is achieved in data storage layer, then write current is reduced to 0.2 mA or less, but manufacturing complexity increases
Solution Approach 1:
The patent employs composite material structures to achieve perpendicular magnetic anisotropy. The data storage layer uses a laminated structure of Co/Ni multilayers with specific thickness ratios, combined with Ru spacer layers and Ta capping layers. This composite structure provides the necessary perpendicular anisotropy through interface effects and magnetoelastic coupling, making the manufacturing process more complex but enabling low write current operation
Solution Approach 2:
The invention applies local quality by creating specific interface structures between different material layers. The perpendicular magnetic anisotropy is generated at the interfaces between Co/Ni layers and Ru spacer layers, rather than uniformly throughout the bulk material. This localized anisotropy at specific interfaces enables the desired magnetic properties while controlling the overall film 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 solution effectively reduces write current to 0.2 mA or less, enhancing scalability and thermal stability, making it suitable for substitution in existing memory technologies.
Implementation Method 1
a data storage layer made of a ferromagnetic material having perpendicular magnetic anisotropy
Implementation Method 2
the magnetization of the first magnetic layer can be reversed by an interaction between spin-polarized conduction electrons and localized electrons in the first magnetic layer
Implementation Method 3
A magnetization state of the data storage layer is changed by current driven domain wall motion
Data Source
AI summary
A magnetic memory according to the present invention has: a first underlayer; a second underlayer so formed on the first underlayer as to be in contact with the first underlayer; and a data storage layer so formed on the second underlayer as to be in contact with the second underlayer. The data storage layer is made of a ferromagnetic material having perpendicular magnetic anisotropy. A magnetization state of the data storage layer is changed by current driven domain wall motion.