Perpendicular MTJ with Enhancement Layers for Thermal Stability
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Solution Overview
Problem
Spin transfer torque magnetic random access memory (STT-MRAM) devices face challenges in achieving thermal stability and scalability, particularly as the size of the perpendicular magnetic tunnel junction (MTJ) is miniaturized, leading to degradation in thermal stability and increased power consumption.
Innovation Solution
The introduction of a non-magnetic seed layer and cap layer with a magnetic tunnel junction (MTJ) structure that includes a magnetic free layer and a magnetic reference layer separated by a non-magnetic perpendicular enhancement layer, along with an anti-ferromagnetic coupling layer and a magnetic fixed layer, enhances the perpendicular anisotropy and thermal stability of the MTJ memory element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the size of the perpendicular magnetic tunnel junction (MTJ) is miniaturized, then the current required to switch the magnetization direction is reduced and power consumption decreases, but the thermal stability of the magnetic layers degrades
Solution Approach 1:
The patent employs composite material structures including perpendicular enhancement layers composed of alternating magnetic and non-magnetic layers (e.g., CoFeB/Pt, CoFeB/Ru), and multi-layer reference structures with anti-ferromagnetic coupling layers. These composite structures provide both the necessary perpendicular magnetic anisotropy for low-power switching and enhanced thermal stability through interfacial anisotropy and exchange coupling mechanisms.
Solution Approach 2:
The patent utilizes parameter changes in material composition and layer thickness to optimize performance. By adjusting the thickness of perpendicular enhancement layers, magnetic layer compositions, and interfacial structures, the patent achieves balanced thermal stability and switching characteristics. The anti-ferromagnetic coupling layer thickness and material composition are specifically tuned to provide desired exchange bias and thermal stability.
2Productivity
If the size of the perpendicular magnetic tunnel junction (MTJ) is miniaturized, then device scalability improves, but the thermal stability and data retention capability deteriorate
Solution Approach 1:
The patent employs composite material structures including perpendicular enhancement layers composed of alternating magnetic and non-magnetic layers (e.g., CoFeB/Pt, CoFeB/Ru), and multi-layer reference structures with anti-ferromagnetic coupling layers. These composite structures provide both the necessary perpendicular magnetic anisotropy for low-power switching and enhanced thermal stability through interfacial anisotropy and exchange coupling mechanisms.
Solution Approach 2:
The patent applies local quality enhancement by introducing perpendicular enhancement layers specifically at critical interfaces where magnetic anisotropy is needed, and anti-ferromagnetic coupling layers locally at the reference layer structure. This targeted approach enhances thermal stability and data retention in miniaturized devices without requiring uniform thickening of all layers, thus maintaining scalability.
3Stability of the object's composition
If a complex multi-layer structure with perpendicular enhancement layers and anti-ferromagnetic coupling layers is introduced, then thermal stability and perpendicular anisotropy are enhanced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent segments the magnetic reference layer into multiple sub-layers separated by anti-ferromagnetic coupling layers, and divides perpendicular enhancement functionality into distinct alternating magnetic and non-magnetic layers. This segmentation allows independent optimization of each layer's thickness and composition, facilitating precise control of thermal stability and perpendicular anisotropy while enabling modular manufacturing approaches.
Solution Approach 2:
The patent utilizes parameter changes in material composition and layer thickness to optimize performance. By adjusting the thickness of perpendicular enhancement layers, magnetic layer compositions, and interfacial structures, the patent achieves balanced thermal stability and switching characteristics. The anti-ferromagnetic coupling layer thickness and material composition are specifically tuned to provide desired exchange bias and thermal stability.
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 improves the thermal stability and scalability of STT-MRAM devices, maintaining data retention and reducing power consumption while allowing for cost-effective manufacturing.
Implementation Method 1
The magnetic free layer structure has a variable magnetization direction substantially perpendicular to the layer plane thereof. The magnetic reference layer structure includes a first magnetic reference layer formed adjacent to the insulating tunnel junction layer and a second magnetic reference layer separated from the first magnetic reference layer by a first non-magnetic perpendicular enhancement layer. The first and second magnetic reference layers have a first fixed magnetization direction substantially perpendicular to the layer planes thereof.
Implementation Method 2
The MTJ structure may further comprise an anti-ferromagnetic coupling layer formed adjacent to the second magnetic reference layer and a magnetic fixed layer formed adjacent to the anti-ferromagnetic coupling layer with the magnetic fixed layer having a second fixed magnetization direction that is perpendicular to the layer plane thereof and is substantially opposite to the first fixed magnetization direction.
Implementation Method 3
A STT-MRAM device normally comprises an array of memory cells, each of which includes at least a magnetic memory element and a selection element coupled in series between appropriate electrodes. Upon application of an appropriate voltage or current to the magnetic memory element, the electrical resistance of the magnetic memory element would change accordingly, thereby switching the stored logic in the respective memory cell.
Data Source
AI summary
The present invention is directed to an MRAM element comprising a magnetic free layer structure and a magnetic reference layer structure with an insulating tunnel junction layer interposed therebetween. The magnetic free layer structure has a variable magnetization direction substantially perpendicular to the layer plane thereof. The magnetic reference layer structure includes a first magnetic reference layer formed adjacent to the insulating tunnel junction layer and a second magnetic reference layer separated from the first magnetic reference layer by a first non-magnetic perpendicular enhancement layer. The first and second magnetic reference layers have a first fixed magnetization direction substantially perpendicular to the layer plane thereof. The second magnetic reference layer has a multilayer structure comprising a first magnetic reference sublayer formed adjacent to the first non-magnetic perpendicular enhancement layer and a second magnetic reference sublayer separated from the first magnetic reference sublayer by an intermediate metallic layer.