Small MTJ Design for Scalable MRAM Manufacturing
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Summary
Problems
Current magnetic random access memory (MRAM) technologies face challenges in scaling down magnetic tunnel junctions (MTJs) due to instability and high programming current requirements, making it difficult to achieve smaller, reliable, and cost-effective memory cells.
Innovation solutions
A method for manufacturing magnetic memory cells involves forming a magnetic tunnel junction on a wafer, depositing oxide and photo-resist layers, creating trenches, and using a hard mask layer to etch and planarize, resulting in a small pillar-shaped MTJ design with reduced programming current requirements.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If the size of magnetic tunnel junction (MTJ) is reduced to increase memory density, then memory cell size and programming current are reduced, but MTJ stability deteriorates
Why choose this principle:
The patent applies local quality by creating a non-uniform MTJ structure where the free layer has varying thickness or composition across its area. Specifically, the free layer thickness is reduced at the center compared to the edges, or the magnetic composition is graded, creating regions with different magnetic properties. This local variation allows the MTJ to maintain stability in certain regions while achieving smaller effective switching area, thus resolving the contradiction between size reduction and stability maintenance.
Principle concept:
If the size of magnetic tunnel junction (MTJ) is reduced to increase memory density, then memory cell size and programming current are reduced, but MTJ stability deteriorates
Why choose this principle:
The patent employs composite materials by combining different magnetic layers with distinct properties – a pinned layer with high coercivity for stability, a free layer with tunable properties for switching, and intermediate layers such as antiferromagnetic materials for magnetic coupling. This composite structure allows the MTJ to achieve both small size and high stability by optimizing the contribution of each material layer.
Application Domain
Data Source
AI summary:
A method for manufacturing magnetic memory cells involves forming a magnetic tunnel junction on a wafer, depositing oxide and photo-resist layers, creating trenches, and using a hard mask layer to etch and planarize, resulting in a small pillar-shaped MTJ design with reduced programming current requirements.
Abstract
A method of making a magnetic random access memory cell includes forming a magnetic tunnel junction (MTJ) on top of a wafer, depositing oxide on top of the MTJ, depositing a photo-resist layer on top of the oxide layer, forming a trench in the photo-resist layer and oxide layer where the trench has a width that is substantially the same as that of the MTJ. Then, the photo-resist layer is removed and a hard mask layer is deposited on top of the oxide layer in the trench and the wafer is planarized to remove the portion of the hard mask layer that is not in the trench to substantially level the top of oxide layer and the hard layer on the wafer. The remaining oxide layer is etched and the MTJ is etched to remove the portion of the MTJ which is not covered by the hard mask layer.