Magnetic Memory Sidewall Oxidation for Electrical Short Prevention
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Solution Overview
Problem
The scalability and practical application of spin injection writing type magnetic memory are hindered by challenges in processing the magnetoresistive element, particularly in preventing electrical short failures and variance in MR ratios due to the complexity of the lamination structure and oxidation of metal layers.
Innovation Solution
A magnetic memory structure and manufacturing method involving a lamination structure with specific metal layers and etching processes, where the second metal layer with easily oxidizable metal is etched last to form a re-deposition layer that can be completely oxidized, preventing electrical shorts and ensuring equal widths of magnetic layers, thereby reducing MR ratio variance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the magnetoresistive element uses a lamination structure with multiple metal layers, then the device functionality is improved, but the manufacturing complexity and risk of electrical short failures increase
Solution Approach 1:
The patent segments the metal layers into distinct groups: a first metal layer (e.g., Ta, W, Ru) that serves as a barrier layer, and a second metal layer (e.g., Al, Cu, Ag) that is etched last to form the re-deposition layer. This segmentation allows each layer to have optimized properties for its specific function, reducing manufacturing complexity while maintaining device functionality.
Solution Approach 2:
The patent applies preliminary action by forming the re-deposition layer from the second metal layer before final device assembly. The second metal layer is designed to be etched last, creating a re-deposition layer that prevents electrical short failures between the first and third metal layers, thereby proactively solving the electrical short problem before it can affect device operation.
2Reliability
If the second metal layer is etched last to form a re-deposition layer, then electrical short failures are prevented, but the etching process complexity increases
Solution Approach 1:
The patent applies local quality by making the second metal layer locally distinct through its material composition (e.g., Al, Cu, Ag) and positioning (between the first and third metal layers). This local differentiation allows the second metal layer to be selectively etched last, forming the re-deposition layer that prevents electrical shorts, while the rest of the structure maintains standard fabrication processes.
3Reliability
If the magnetic layers are made with equal widths, then the MR ratio variance is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies self-service through the re-deposition layer mechanism. The second metal layer, being etched last, naturally forms a re-deposition layer that equalizes the widths of the first and third metal layers. This self-adjusting mechanism reduces MR ratio variance without requiring additional precision control steps, as the structure itself compensates for width variations.
4Reliability
If the second metal layer contains easily oxidizable metal, then the re-deposition layer can be completely oxidized to prevent electrical shorts, but the oxidation process control becomes more difficult
Solution Approach 1:
The patent applies parameter changes by selecting specific materials for the second metal layer (e.g., Al, Cu, Ag) that have controlled oxidation characteristics. These materials can be completely oxidized under standard oxidation conditions to form insulating re-deposition layers, preventing electrical shorts. The oxidation process is simplified by choosing materials whose oxidation parameters fall within standard processing ranges.
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 prevents electrical short failures and reduces variance in MR ratios, resulting in a magnetic memory with high reliability and ideal shape, improving the scalability and practicality of spin injection writing type magnetic memory.
Implementation Method 1
the second metal layer having a first sidewall portion which contacts the first metal layer, and the second metal layer having a second sidewall portion above the first sidewall portion, the second sidewall portion which steps back from the first sidewall portion
Implementation Method 2
current necessary for magnetization reversal or a Magnetoresistive element is defined by a current density
Data Source
AI summary
According to one embodiment, a magnetic memory includes a first metal layer including a first metal, a second metal layer on the first metal layer, the second metal layer including a second metal which is more easily oxidized than the first metal, the second metal layer having a first sidewall portion which contacts the first metal layer, and the second metal layer having a second sidewall portion above the first sidewall portion, the second sidewall portion which steps back from the first sidewall portion, a magnetoresistive element on the second metal layer, a third metal layer on the magnetoresistive element, and a first material which contacts a sidewall portion of the magnetoresistive element and the second sidewall portion of the second metal layer, the first material including an oxide of the second metal.