MTJ Device Oxidized Sidewalls Reduce Stray Fields
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Solution Overview
Problem
Conventional magnetic tunnel junction (MTJ) devices face issues with stray fields and reliability due to the lack of effective control over the magnetic moment alignment between the fixed and free magnetic layers, leading to instability in resistance values used for data storage.
Innovation Solution
A manufacturing method for MTJ devices that includes forming a free layer with a spacer sandwiched by ferromagnetic layers, where selective oxidation is used to create oxidized sidewall parts, reducing stray fields and enhancing device reliability by stabilizing the magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MTJ structure is used without oxidized sidewall parts, then manufacturing process is simpler, but stray field increases and device reliability deteriorates
Solution Approach 1:
The free layer is segmented into multiple ferromagnetic layers with spacer layers in between, creating a multi-layered structure. This segmentation allows for better control of magnetic properties and reduction of stray field, improving device reliability despite increased structural complexity
Solution Approach 2:
The patent uses composite material structure combining ferromagnetic layers with spacer layers, where each layer has distinct magnetic properties. The composite structure enables optimization of magnetic moment alignment and stray field control, achieving improved reliability
2Manufacturing precision
If magnetic moment alignment between fixed and free layers is not controlled, then manufacturing process is easier, but resistance value stability deteriorates
Solution Approach 1:
Different regions of the free layer are given different magnetic properties through the spacer layer configuration. The local magnetic characteristics are optimized to achieve precise magnetic moment alignment, improving resistance value stability while maintaining manufacturing feasibility
Solution Approach 2:
The patent controls magnetic moment alignment by changing parameters such as layer thickness, material composition, and oxidation state of sidewall parts. These parameter adjustments enable precise control of magnetic properties during manufacturing
3Reliability
If stray field is not reduced, then device structure remains simple, but resistance value stability deteriorates
Solution Approach 1:
Spacer layers act as intermediary elements between ferromagnetic layers, mediating the magnetic interaction and reducing stray field effects. This intermediary structure improves resistance value stability while managing the complexity through functional design
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 method results in a magnetic tunnel junction with a step-shaped magnetic part, exhibiting lower stray fields and improved reliability, allowing for stable resistance-based data storage.
Implementation Method 1
A selective oxidation process is performed to only oxidize the first ferromagnetic layer, the spacer and the Second ferromagnetic layer, to form oxidized spacer sidewall parts of the spacer, first oxidized sidewall parts of the first ferromagnetic layer, and second oxidized sidewall parts of the second ferromagnetic layer
Data Source
AI summary
A magnetic tunnel junction (MTJ) device includes a bottom electrode, a reference layer, a tunnel barrier layer, a free layer and a top electrode. The bottom electrode and the top electrode are facing each other. The reference layer, the tunnel barrier layer and the free layer are stacked from the bottom electrode to the top electrode, wherein the free layer includes a first ferromagnetic layer, a spacer and a second ferromagnetic layer, wherein the spacer is sandwiched by the first ferromagnetic layer and the second ferromagnetic layer, wherein the spacer includes oxidized spacer sidewall parts, the first ferromagnetic layer includes first oxidized sidewall parts, and the second ferromagnetic layer includes second oxidized sidewall parts. The present invention also provides a method of manufacturing a magnetic tunnel junction (MTJ) device.