Hybrid Magnetization Layer for High-Temperature STT-MRAM Stability
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Solution Overview
Problem
Magnetic devices with perpendicular magnetic anisotropy (PMA) face challenges in maintaining stability at high temperatures and achieving low-current operations while securing a high tunneling magneto-resistance (TMR) ratio.
Innovation Solution
A magnetic device is designed with a hybrid magnetization layer comprising a first PMA layer, a second PMA layer, and an amorphous blocking layer, where the first PMA layer includes alternately stacked Co and Pt or Pd layers with a dopant, and the second PMA layer includes Co, Fe, or Ni with a second dopant, allowing for different crystal-oriented structures and enabling high heat resistance and low-current operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a magnetic layer with perpendicular magnetic anisotropy is used to achieve high integration in STT-MRAM, then device integration density is improved, but maintaining stable PMA at high temperatures becomes difficult
Solution Approach 1:
The patent employs a composite magnetization layer structure consisting of multiple PMA layers (first and second PMA layers) with different crystal orientations separated by an amorphous blocking layer. This composite structure combines the advantages of different materials and structures to achieve both high integration density and thermal stability, resolving the contradiction between integration density and PMA stability at high temperatures.
Solution Approach 2:
The magnetization layer is segmented into multiple functional sub-layers: a first PMA layer with L11 or L10 atomic ordering providing heat-resistant PMA, an amorphous blocking layer preventing crystal growth, and a second PMA layer with different crystal orientation providing additional PMA contribution. This segmentation allows each layer to perform its specific function optimally while working together to maintain stable PMA at high temperatures.
2Speed
If current is increased to achieve fast switching in STT-MRAM, then switching speed is improved, but operational current consumption increases
Solution Approach 1:
The patent modifies the magnetic anisotropy parameters by introducing dopants (such as B, C, N, or O) into the PMA layers and adjusting the thickness and composition ratios of different layers. These parameter changes optimize the perpendicular magnetic anisotropy energy, enabling fast switching at lower current densities and thus reducing operational current consumption while maintaining high switching speed.
Solution Approach 2:
The composite structure of multiple PMA layers with different crystal orientations and an amorphous blocking layer creates optimized magnetic properties that reduce the switching current density. The synergistic effect of different materials and structures enables fast switching at lower currents, resolving the contradiction between switching speed and current consumption.
3Device complexity
If a single PMA layer structure is used to simplify device structure, then device complexity is reduced, but achieving both heat resistance and high TMR ratio becomes difficult
Solution Approach 1:
The magnetization layer is divided into functionally distinct segments: the first PMA layer optimized for heat resistance with specific crystal orientation, the amorphous blocking layer for structural stability and preventing unwanted crystal growth, and the second PMA layer for additional magnetic anisotropy contribution. This segmentation achieves both heat resistance and high TMR ratio while maintaining a relatively straightforward fabrication process.
Solution Approach 2:
Different regions of the magnetization layer structure are assigned different local properties: the first PMA layer has L11 or L10 atomic ordering for heat resistance, the blocking layer has amorphous structure for stability, and the second PMA layer has different crystal orientation for magnetic properties. This local differentiation of properties enables the structure to simultaneously achieve heat resistance and high TMR ratio.
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 magnetic device effectively maintains perpendicular magnetic anisotropy at high temperatures and achieves a high TMR ratio, enabling efficient and stable low-current operations.
Implementation Method 1
a first PMA layer, a second PMA layer, and an amorphous blocking layer disposed between the first PMA layer and the second PMA layer
Implementation Method 2
The first PMA layer may have a hexagonal closest packing (HCP) (001) crystal-oriented structure, and the second PMA layer may have a body-centered cubic (BCC) (001) crystal-oriented structure
Implementation Method 3
a tunnel barrier disposed between the free layer and the pinned layer
Data Source
AI summary
A magnetic device can include a tunnel bather and a hybrid magnetization layer disposed adjacent the tunnel barrier. The hybrid magnetization layer can include a first perpendicular magnetic anisotropy (PMA) layer, a second PMA layer, and an amorphous blocking layer disposed between the first and second PMA layers. The first PMA layer can include a multi-layer film in which a first layer formed of Co and a second layer formed of Pt or Pd are alternately stacked. A first dopant formed of an element different from those of the first and second layers can also be included in the first PMA layer. The second PMA layer can be disposed between the first PMA layer and the tunnel barrier, and can include at least one element selected from a group consisting of Co, Fe, and Ni.