Magnetic Tunnel Junction Self-Alignment in Domain Wall Shift Registers
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Solution Overview
Problem
Existing magnetic domain wall shift register memory devices face challenges in accurately aligning magnetic tunnel junctions (MTJs) with nanowires, leading to alignment mismatches and increased process complexity due to the need for narrower MTJs and separate lithography steps.
Innovation Solution
A self-alignment method for magnetic tunnel junctions is developed, where a lithographic strip is patterned on a magnetic material, and a nanowire and magnetic reference layer island are etched to form a self-aligned MTJ interface matching the nanowire width, eliminating the need for pre-existing MTJ structures and reducing alignment errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate lithography steps are used to pattern the reference magnetic layer and nanowire, then the fabrication process can be completed, but alignment accuracy deteriorates and process complexity increases
Solution Approach 1:
The patent combines the patterning of the reference magnetic layer and the nanowire into a single lithography step. By using one lithographic pattern to define both structures simultaneously, the method eliminates alignment errors between separate steps and reduces process complexity while maintaining fabrication flexibility.
2Manufacturing precision
If the MTJ is made narrower than the nanowire to improve alignment, then alignment precision may improve, but device functionality deteriorates due to rounding effects and optical limitations
Solution Approach 1:
The patent performs preliminary patterning of both the reference magnetic layer and nanowire in a single lithography step, establishing their relative positions before any etching or fabrication variations occur. This preliminary action prevents the need to make the MTJ narrower as a compensation strategy, allowing the MTJ to maintain its full width and optimal functionality.
3Manufacturing precision
If trial-and-error process optimization is used to achieve proper alignment, then alignment accuracy can be improved, but fabrication time and cost increase
Solution Approach 1:
By merging the patterning of the reference magnetic layer and nanowire into a single lithography step, the patent eliminates the need for trial-and-error optimization between multiple steps. The alignment is built-in from the start, allowing for straightforward, efficient fabrication without iterative adjustments.
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 enhances the accuracy and reproducibility of MTJ alignment, increases yield, and allows for the fabrication of multiple self-aligned MTJs on multiple nanowires using a single extended lithographic structure, reducing fabrication complexities and errors.
Implementation Method 1
an interface between the magnetic nanowire and the magnetic reference layer island is an magnetic tunnel junction aligned with a width of the nanowire
Data Source
AI summary
A method of fabricating a self-aligning magnetic tunnel junction the method includes patterning a lithographic strip on a second magnetic material deposited on a first magnetic material that is disposed on a substrate, forming a top magnetic strip by etching an exposed portion of the second magnetic material, patterning a nanowire and a magnetic reference layer island over the substrate and forming the nanowire and the magnetic reference layer island by etching an exposed portion of the first magnetic layer and an exposed portion of the top magnetic strip, wherein an interface between the magnetic nanowire and the magnetic reference layer island is an magnetic tunnel junction aligned with a width of the nanowire.