Magnetic Element Perpendicular Anisotropy Thermal Stability
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Solution Overview
Problem
Spin torque magnetization reversal in MRAMs faces challenges in maintaining thermal stability while reducing the volume of the storage layer, leading to potential writing errors due to heat fluctuations and increased power consumption.
Innovation Solution
A storage element with a first layer of approximately 45 nm or less in transverse length and 2,390 nm^3 or less in volume, coupled with an insulation layer of non-magnetic material like MgO, and a second layer with fixed magnetization, allowing electrons to reach the first layer before entering a non-polarized state, enhancing thermal stability and reducing writing current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the volume of the storage layer is reduced to miniaturize the device, then device size and power consumption are improved, but thermal stability deteriorates leading to writing errors
Solution Approach 1:
The patent changes the magnetic anisotropy parameter from in-plane to perpendicular magnetization by modifying the storage layer composition (e.g., using CoFeB, CoFe, or CoNi alloys) and interface engineering with adjacent layers. This parameter change enables thermal stability to be maintained at smaller volumes by increasing the energy barrier for magnetization reversal, thus preventing writing errors due to heat fluctuations while achieving device miniaturization.
Solution Approach 2:
The patent employs composite magnetic layer structures combining multiple materials (e.g., CoFeB/MgO, CoFe/Ta, CoNi/AlOx) with specific thickness ratios. These composite structures create perpendicular magnetic anisotropy through interface effects and magnetostriction, enabling the storage layer to maintain high thermal stability at reduced volumes. The composite design allows optimization of both volume and thermal stability simultaneously.
2Use of energy by moving object
If spin torque magnetization reversal is used to reduce writing current, then power consumption is improved, but thermal stability maintenance becomes difficult at small scales
Solution Approach 1:
The patent changes the magnetization reversal mechanism parameter from current magnetic field (XMR) to spin transfer torque (STT) by optimizing the storage layer thickness to 3-10 nm and using spin-polarized electron injection. This enables lower writing currents while maintaining thermal stability through perpendicular magnetic anisotropy, resolving the contradiction between energy efficiency and reliability at small scales.
Solution Approach 2:
The patent replaces the mechanical/current magnetic field reversal mechanism with a quantum mechanical spin torque mechanism. By utilizing spin-polarized electrons to exert torque on the storage layer magnetization, the system achieves reversal at lower currents while the perpendicular anisotropy provides thermal stability, substituting a less efficient mechanical field approach with a more efficient quantum spin approach.
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 ensures stable thermal stability, miniaturization, and low power consumption, preventing operation errors and reducing overall power consumption in ST-MRAMs.
Implementation Method 1
a storage layer storing a magnetization state of a ferromagnetic layer as information
Implementation Method 2
a magnetization fixing layer in which the direction of magnetization is fixed
Implementation Method 3
allowing electrons passing through the second layer reach the first layer before the electrons enter a non-polarized state
Data Source
AI summary
A magnetic element is provided. The magnetic element includes a free magnetization layer having a surface area that is approximately 1,600 nm2 or less, the free magnetization layer including a magnetization state that is configured to be changed; an insulation layer coupled to the free magnetization layer, the insulation layer including a non-magnetic material; and a magnetization fixing layer coupled to the insulation layer opposite the free magnetization layer, the magnetization fixing layer including a fixed magnetization so as to be capable of serving as a reference of the free magnetization layer.