Magnetic Memory Element With Step Formation Layer
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Solution Overview
Problem
Current magnetic memory technologies face challenges in miniaturization and scalability due to high writing currents required for domain wall motion, which affect thermal stability and reliability, and existing methods like spin transfer magnetization switching have limitations in practical implementation.
Innovation Solution
A magnetic memory element with a ferromagnetic layer having perpendicular magnetic anisotropy, incorporating a step formation layer under the magnetization free layer to effectively trap domain walls, allowing for precise control of domain wall position and reduced writing currents through current-induced domain wall motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a magnetic field is used to switch magnetization direction for high-speed writing, then writing speed is improved (1 nano-second or less), but writing current increases to a few mA and chip area becomes large
Solution Approach 1:
The patent replaces the magnetic field-based writing mechanism with a spin transfer torque mechanism. Instead of using a magnetic field generated by current through a wiring line, the invention uses spin-polarized electrons to directly switch magnetization in the storage layer through spin transfer torque, eliminating the need for peripheral writing wiring and reducing writing current requirements
Solution Approach 2:
The patent introduces local structural variations including a step formation layer with different etching rates, magnetic charge accumulation regions, and localized magnetization patterns. These local structural differences create regions with enhanced spin transfer torque efficiency, allowing magnetization switching at lower current densities
2Area of moving object
If the size of the memory cell is miniaturized, then integration density is improved, but writing current further increases and scaling becomes difficult
Solution Approach 1:
The patent changes the magnetization switching mechanism from magnetic field-driven to spin transfer torque-driven, and introduces perpendicular magnetic anisotropy through compositional changes in the magnetic layers. These parameter changes enable scaling to smaller dimensions while maintaining or reducing writing current requirements
Solution Approach 2:
The patent transitions from in-plane magnetization to perpendicular magnetization, utilizing the out-of-plane dimension for magnetization orientation. This dimensional change enables better scaling behavior as the magnetization switching becomes less sensitive to lateral dimension reduction
3Area of moving object
If spin transfer magnetization switching is used for scaling, then writing current decreases with element size reduction, but a relatively large current must flow through the insulating film causing reliability issues
Solution Approach 1:
The patent introduces a step formation layer as an intermediary structure between the storage layer and the insulating film. This step formation layer with different etching rates creates a localized region that concentrates spin transfer torque while protecting the insulating film from excessive current stress, thereby improving reliability
Solution Approach 2:
The patent creates multiple magnetic charge accumulation regions and uses patterned magnetization structures that replicate the spin transfer torque effect across different locations. This allows the writing current to be distributed and optimized, reducing the peak current through any single insulating film region
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 proposed solution enhances the retention properties of magnetic memory and reduces writing current variations by providing precise domain wall pinning sites, enabling stable data storage and efficient data writing in a scalable and reliable manner.
Implementation Method 1
the magnetization in the first magnetic layer (magnetization free layer) is switched by using an interaction between spin-polarized conduction electrons and localized electrons in the first magnetic layer (magnetization free layer) when a current flows between the second magnetic layer (reference layer) and the first magnetic layer (magnetization free layer)
Implementation Method 2
A reading operation is carried out by using a magnetoresistive effect generated between the first magnetic layer (magnetization free layer) and the second magnetic layer (reference layer)
Implementation Method 3
a step formation layer configured to be provided under the first magnetization free layer, wherein the first magnetization free layer has at least one of a step, a groove and a protrusion inside
Data Source
AI summary
A magnetic memory element includes: a first magnetization free layer configured to be composed of ferromagnetic material with perpendicular magnetic anisotropy; a reference layer configured to be provided near the first magnetization free layer; a non-magnetic layer configured to be provided adjacent to the reference layer; and a step formation layer configured to be provided under the first magnetization free layer. The first magnetization free layer includes: a first magnetization fixed region of which magnetization is fixed, a second magnetization fixed region of which magnetization is fixed, and a magnetization free region configured to be connected with the first magnetization fixed region and the second magnetization fixed region. The first magnetization free layer has at least one of a step, a groove and a protrusion inside.