CoFeB ST-MRAM Memory Element with Oxide Layers
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Solution Overview
Problem
Spin Torque-Magnetic Random Access Memory (ST-MRAM) faces challenges in reducing switching current and ensuring thermal stability while miniaturizing, as the current required for magnetization switching exceeds the saturation current of selection transistors and can lead to insulation breakdown and thermal instability, affecting data retention.
Innovation Solution
A memory element with a layered structure comprising a Co—Fe—B magnetic layer, a first oxide layer as a tunnel barrier, and a Li-based oxide layer on the opposite side, which enhances perpendicular magnetic anisotropy, allowing for reduced switching current and improved thermal stability through spin torque magnetization switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a current magnetic field is used for magnetization switching in MRAM, then high-speed operation and unlimited rewriting are achieved, but power consumption increases and cell structure becomes complex due to word lines
Solution Approach 1:
The patent replaces the magnetic field-based switching mechanism (mechanical/electromagnetic system) with a spin torque-based switching mechanism (quantum mechanical effect). By using spin-polarized electrons to exert torque on the magnetic moment, the invention eliminates the need for word lines and current magnetic fields, thereby reducing power consumption while maintaining high-speed operation capabilities
Solution Approach 2:
The patent changes the fundamental switching parameter from magnetic field strength to spin torque magnitude. By controlling the spin polarization and current density, the invention achieves magnetization switching with lower energy consumption, transforming the operational parameters of the memory cell to improve energy efficiency
2Speed
If a current magnetic field is used for magnetization switching in MRAM, then high-speed operation is achieved, but the cell structure becomes simple less due to necessary word lines
Solution Approach 1:
The patent replaces the magnetic field-based switching mechanism (mechanical/electromagnetic system) with a spin torque-based switching mechanism (quantum mechanical effect). By using spin-polarized electrons to exert torque on the magnetic moment, the invention eliminates the need for word lines and current magnetic fields, thereby reducing power consumption while maintaining high-speed operation capabilities
Solution Approach 2:
The spin injection layer serves multiple functions: it generates spin-polarized electrons, provides spin torque for switching, and acts as part of the conduction path. This multi-functionality reduces the number of separate components needed, simplifying the overall cell structure while maintaining high-speed operation
3Productivity
If the memory element is miniaturized to increase integration density, then capacity increases, but the switching current exceeds the saturation current of selection transistors
Solution Approach 1:
The patent changes the fundamental switching parameter from magnetic field strength to spin torque magnitude. By controlling the spin polarization and current density, the invention achieves magnetization switching with lower energy consumption, transforming the operational parameters of the memory cell to improve energy efficiency
Solution Approach 2:
The patent introduces a tunnel insulating layer as an intermediary between the spin injection layer and the magnetic moment layer. This tunnel barrier enables spin transfer while blocking charge current, allowing the use of lower currents for switching and improving reliability during miniaturization
4Ease of operation
If high current is applied for magnetization switching, then switching is achieved, but insulation breakdown and thermal instability occur
Solution Approach 1:
The patent introduces a tunnel insulating layer as an intermediary between the spin injection layer and the magnetic moment layer. This tunnel barrier enables spin transfer while blocking charge current, allowing the use of lower currents for switching and improving reliability during miniaturization
Solution Approach 2:
The patent replaces the magnetic field-based switching mechanism (mechanical/electromagnetic system) with a spin torque-based switching mechanism (quantum mechanical effect). By using spin-polarized electrons to exert torque on the magnetic moment, the invention eliminates the need for word lines and current magnetic fields, thereby reducing power consumption while maintaining high-speed operation capabilities
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 decreases the switching current and secures thermal stability, enabling reliable and efficient data storage with reduced power consumption and increased integration density in ST-MRAM.
Implementation Method 1
when spin-polarized electrons passing through a magnetic layer which is fixed in an arbitrary direction enter another free (the direction is not fixed) magnetic layer, a torque (which is also called as a spin transfer torque) is applied to the magnetic layer
Implementation Method 2
A first oxide layer is formed on an interface between the intermediate layer that is contacted with the memory layer and the memory layer. A second oxide layer is formed on an interface between a different layer that is contacted with the memory layer at an opposite side from the intermediate layer and the memory layer
Data Source
AI summary
A memory element has a layered structure, including a memory layer that has magnetization perpendicular to a film face in which a magnetization direction is changed depending on information, and includes a Co—Fe—B magnetic layer, the magnetization direction being changed by applying a current in a lamination direction of the layered structure to record the information in the memory layer, a magnetization-fixed layer having magnetization perpendicular to a film face that becomes a base of the information stored in the memory layer, and an intermediate layer that is formed of a non-magnetic material and is provided between the memory layer and the magnetization-fixed layer, a first oxide layer and a second oxide layer.