Magnetic Memory Device Using Co/Pt and Mo/W Layers
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Solution Overview
Problem
Existing magnetic memory devices face limitations in high integration due to the thickness of the stacked structure, which prevents a narrow interval between adjacent magnetoresistance effect elements, leading to reduced packing density and efficiency.
Innovation Solution
A magnetic memory device with a stacked structure including a Co/Pt multilayer shift canceling layer and a Mo or W-based nonmagnetic layer, where the Co/Pt multilayer has a HCP or FCC structure and the nonmagnetic layer has a BCC structure, enhancing crystallinity and antiferromagnetic coupling, and reducing the overall thickness to allow for closer element integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional buffer layers are used in the stacked structure, then the structure provides basic magnetic layer support, but the overall thickness becomes too large, preventing narrow intervals between adjacent magnetoresistance effect elements
Solution Approach 1:
The patent changes the material composition parameters of the buffer layers, specifically using a CoFeB layer with controlled thickness (0.5-2.0 nm) and magnetization direction, combined with a Ru layer. This parameter optimization reduces the overall thickness while maintaining the necessary magnetic properties and coupling strength.
Solution Approach 2:
The patent employs a composite buffer layer structure consisting of CoFeB (cobalt ferrite boride) and Ru (ruthenium) layers. This composite approach combines the advantages of both materials: CoFeB provides perpendicular magnetic anisotropy and magnetic coupling, while Ru provides structural stability and crystallinity enhancement, achieving both thickness reduction and property maintenance.
2Quantity of substance
If the stacked structure thickness is reduced to increase integration density, then more elements can be integrated, but the perpendicular magnetic anisotropy and MR ratio may deteriorate
Solution Approach 1:
The patent applies local quality by creating a Co/Pt multilayer structure with specific local compositions and thicknesses (Co layer: 0.3-0.7 nm, Pt layer: 0.3-0.7 nm) within the buffer layer region. This localized optimization ensures that the critical area near the magnetoresistance effect element maintains high perpendicular magnetic anisotropy and MR ratio, while other regions can be optimized for thickness reduction.
Solution Approach 2:
The CoFeB layer acts as an intermediary between the Ru buffer layer and the Co/Pt multilayer structure. It mediates the interaction by providing a transition zone that maintains crystallinity from the Ru layer while enabling the formation of the Co/Pt multilayer with the required magnetic properties, thus preserving both thickness reduction and magnetic performance.
3Ease of manufacture
If conventional buffer layer configurations are used, then the structure is simple to manufacture, but interdiffusion occurs between layers, degrading performance
Solution Approach 1:
The Ru layer serves as an intermediary diffusion barrier between the CoFeB layer and the underlying substrate or adjacent layers. Ru has low solubility for cobalt and iron, effectively preventing interdiffusion while maintaining a relatively simple manufacturing process. This intermediary layer preserves composition stability without significantly complicating the fabrication sequence.
Solution Approach 2:
The patent uses thin layers (0.5-2.0 nm for CoFeB, 0.3-0.7 nm for Ru) that are sufficient to prevent interdiffusion and provide necessary magnetic properties but thin enough to minimize material usage and manufacturing complexity. These thin functional layers achieve the required performance without requiring thick, complex structures.
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 configuration enables a higher integration density of magnetoresistance effect elements, improving the perpendicular magnetic anisotropy and MR ratio while inhibiting interdiffusion and reducing the thickness of the buffer layers, allowing for a more compact and efficient magnetic memory device.
Implementation Method 1
the Co/Pt multilayer has a HCP or FCC structure and the nonmagnetic layer has a BCC structure, enhancing crystallinity and antiferromagnetic coupling, and reducing the overall thickness
Implementation Method 2
a second magnetic layer having a fixed magnetization direction; a third magnetic layer having a fixed magnetization direction antiparallel to the magnetization direction of the second magnetic layer
Data Source
AI summary
According to one embodiment, a magnetic memory device includes a first magnetic layer, a second magnetic layer and a third magnetic layer having a fixed magnetization direction antiparallel to a magnetization direction of the second magnetic layer, first, second and third nonmagnetic layers. The firs nonmagnetic layer is between the first and second magnetic layers, the second magnetic layer is between the first nonmagnetic layer and the third magnetic layer, the third magnetic layer is between the second magnetic layer and the second nonmagnetic layer, the third nonmagnetic layer is between the second and the third magnetic layers, the third magnetic layer contains Co and Pt, and the second nonmagnetic layer contains at least one of Mo and W.