Reversed Stack MTJ Free Layer Protection
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Solution Overview
Problem
Conventional manufacturing processes for magnetic tunneling junctions in MRAM cells are prone to plasma damage and contamination of the free layer during etching, leading to defects in the cells.
Innovation Solution
Reversing the order of the film stack to place the free layer on the bottom, allowing for separate etching and forming a protective sidewall barrier to prevent damage and contamination, while also using in situ encapsulation to minimize exposure to the ambient environment during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the conventional film stack order is used with the free layer on top, then the manufacturing process follows traditional sequencing, but the free layer is susceptible to plasma damage and contamination during etching
Solution Approach 1:
The patent inverts the conventional film stack order by placing the free layer at the bottom instead of on top. This reversal allows the free layer to be processed and protected before subsequent etching steps, eliminating plasma damage and contamination issues that occur when the free layer is positioned on top during traditional manufacturing sequences.
2Reliability
If the free layer is etched separately with protective sidewall barriers, then plasma damage and contamination are reduced, but the manufacturing process complexity increases
Solution Approach 1:
The patent forms protective sidewall barriers and performs etching operations on the free layer before processing other layers in the stack. This preliminary action approach allows the free layer to be protected in advance, preventing plasma damage and contamination during subsequent manufacturing steps while maintaining process control.
3Object-affected harmful factors
If in situ encapsulation is used to minimize ambient exposure, then contamination is reduced, but the processing sequence becomes more complex
Solution Approach 1:
The patent employs in situ encapsulation techniques that create a protected environment during processing, minimizing exposure of the free layer and other sensitive layers to ambient contamination. This approach maintains a controlled atmosphere throughout the manufacturing sequence, reducing harmful environmental factors.
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 approach effectively reduces plasma damage and contamination, ensuring reliable data storage by maintaining a significant resistance difference between the two states of the MRAM cells, thus enhancing the performance and reliability of the MRAM cells.
Implementation Method 1
current flows through the insulating barrier by quantum mechanical tunneling
Implementation Method 2
The resistance of the MTJ depends on the relative orientation of magnetic elements in the two ferromagnetic layers
Data Source
AI summary
An integrated circuit device includes a substrate and a magnetic tunneling junction (MTJ). The MTJ includes at least a pinned layer, a barrier layer, and a free layer. The MTJ is formed over a surface of the substrate. Of the pinned layer, the barrier layer, and the free layer, the free layer is formed first and is closest to the surface. This enables a spacer to be formed over a perimeter region of the free layer prior to etching the free layer. Any damage to the free layer that results from etching or other free layer edge-defining process is kept at a distance from the tunneling junction by the spacer.