Magnetic Memory Integration Density via Spin Injection
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Solution Overview
Problem
Current magnetic memory technologies face challenges in enhancing integration density and design/manufacturing margins, particularly in achieving high TMR ratios and reducing the number of external terminals while maintaining effective writing characteristics.
Innovation Solution
The magnetic memory design incorporates a structure with a first magnetic layer, a conductive layer, and a synthetic anti-ferromagnetic (Sy-AF) structure, utilizing a spin injection method for writing and integrating read and write heads, which reduces external terminals and improves integration density by using a spin injection domain wall memory approach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional magnetic memory structure is used, then the basic memory function is achieved, but the integration density is limited and the number of external terminals remains high
Solution Approach 1:
The patent combines the read head and write head into a single integrated structure, eliminating the need for separate read and write terminals. The magnetic tunnel junction (MTJ) element serves dual purposes for both reading and writing operations, reducing the total number of external terminals required while increasing integration density.
Solution Approach 2:
The magnetic tunnel junction element is designed to perform multiple functions: it serves as both the storage element and the sensing element. The same MTJ structure is used for both write operations (via spin transfer torque) and read operations (via tunnel magnetoresistance), making the device multi-functional and reducing terminal requirements.
2Measurement precision
If the TMR ratio is increased to improve reading sensitivity, then the read margin is improved, but the manufacturing precision requirements become more stringent
Solution Approach 1:
The patent optimizes the thickness parameters of the magnetic layers and tunnel barrier to achieve high TMR ratio. By carefully controlling the thickness of the CoFeB layer, MgO tunnel barrier, and other magnetic layers, the design achieves enhanced tunnel magnetoresistance while maintaining manufacturability through well-defined parameter ranges.
Solution Approach 2:
The patent uses composite magnetic structures including CoFeB (cobalt ferrite boride), CoFe (cobalt ferrite), and MgO (magnesium oxide) layers. These composite materials provide both high TMR ratio and robustness against manufacturing variations, as each material contributes specific properties that collectively enhance the overall performance and tolerance to thickness variations.
3Volume of moving object
If the magnetic layer thickness is reduced to improve integration density, then the device size is reduced, but the writing characteristics may be degraded
Solution Approach 1:
The patent uses CoFeB magnetic layers with optimized thickness parameters (e.g., 3-5 nm) that provide sufficient magnetic moment for reliable writing while being thin enough to achieve high integration density. The specific composition and thickness parameters are tuned to maintain adequate spin polarization and magnetic anisotropy even at reduced thicknesses.
Solution Approach 2:
The patent utilizes spin transfer torque (STT) which relies on the phase transition of electron spin states as they traverse the magnetic layers. By controlling the current density and the magnetic layer properties, the system can reliably switch the magnetization state even in thin layers, maintaining writing characteristics while achieving high integration density.
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 design enhances integration density, enlarges the design/manufacturing margin, and maintains effective writing characteristics by reducing the number of external terminals and improving the TMR ratio without degrading writing performance.
Implementation Method 1
Three-terminal type magnetic random access memory using a torque originating spin-orbit interaction has been proposed
Implementation Method 2
improving the TMR ratio without degrading writing performance
Implementation Method 3
utilizing a spin injection method for writing
Data Source
AI summary
According to one embodiment, a magnetic memory includes a structure body including a first magnetic layer and a conductive layer, a second magnetic layer, a first electrode, a second electrode, a third magnetic layer, an intermediate layer, a third electrode, a fourth magnetic layer, and a circuit element. The first magnetic layer is disposed between the second magnetic layer and the conductive layer. The first electrode is connected to a first portion of the structure body. The intermediate layer is provided between the third magnetic layer and the second magnetic layer. The circuit element includes a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer. The first semiconductor layer is connected to the first electrode. The second semiconductor layer is connected to the third magnetic layer. The third semiconductor layer is connected to the first semiconductor layer and the second semiconductor layer.