Co/Ni Multilayer Seed Layer for Magnetic Anisotropy
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Solution Overview
Problem
Current magnetic device technologies, such as MRAM and MAMR, face challenges with high switching current density and low magnetic anisotropy, limiting their performance and scalability, particularly due to the high cost and impractical annealing requirements of existing (Co/Pt)Y and (Co/Pd)Y multilayer stacks.
Innovation Solution
A multilayer stack comprising a composite seed layer with a Ta/Ti/Cu configuration, subjected to plasma treatment and natural oxidation, enhances the interface smoothness and spin-orbit interactions, allowing for a (Co/Ni)X or (CoFe/Ni)X laminate with improved magnetic anisotropy and coercivity, achieving higher spin polarization and reduced critical current density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If (Co/Pt)Y or (Co/Pd)Y multilayer stacks are used to achieve high perpendicular magnetic anisotropy, then magnetic anisotropy is improved, but material cost increases and annealing requirements become more stringent
Solution Approach 1:
The patent replaces expensive Pt or Pd materials with cheaper Co/Ni or CoFe/Ni multilayer stacks that can achieve comparable or superior PMA without requiring stringent annealing conditions, effectively using more economical materials to achieve the same functional goal
Solution Approach 2:
The patent changes the material composition parameters from traditional (Co/Pt)Y or (Co/Pd)Y stacks to (Co/Ni)X or (CoFe/Ni)X laminates with specific thickness ratios (X between 5-50), achieving high PMA through compositional optimization rather than relying on expensive materials and high-temperature annealing
2Use of energy by moving object
If switching current density is reduced for low-power devices, then energy consumption is improved, but magnetic anisotropy must be increased which complicates the structure
Solution Approach 1:
The patent divides the magnetic layer into multiple thin alternating layers of Co/Ni or CoFe/Ni with specific thicknesses (e.g., 2-5 nm Co layers and 3-8 nm Ni layers), where each interface contributes to the overall perpendicular magnetic anisotropy, enabling high PMA and low switching current without requiring a single complex material
Solution Approach 2:
The patent creates a composite multilayer structure where alternating ferromagnetic (Co or CoFe) and non-magnetic (Ni) layers work together to generate enhanced perpendicular magnetic anisotropy through spin-orbit coupling at interfaces, achieving low switching current density without excessive structural complexity
3Area of moving object
If cell size is reduced for higher density, then packing density is improved, but thermal stability decreases requiring larger magnetic anisotropy
Solution Approach 1:
The patent optimizes the thickness parameters of individual layers in the (Co/Ni)X or (CoFe/Ni)X laminate (e.g., Co layer thickness of 2-5 nm, Ni layer thickness of 3-8 nm) to maximize perpendicular magnetic anisotropy per unit volume, enabling high thermal stability even in miniaturized cells
Solution Approach 2:
The patent transitions from in-plane magnetization to perpendicular magnetization by engineering the multilayer structure, which provides significantly larger magnetic anisotropy energy that scales better with reduced cell volume, thereby maintaining thermal stability at higher densities
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
The solution provides a high-performance, low-cost alternative with increased coercivity and spin polarization, enabling wider acceptance and improved thermal stability in magnetic device applications, while reducing the need for expensive materials and stringent annealing conditions.
Implementation Method 1
the top surface of the seed layer has been modified by a plasma treatment or oxidized to form an OSL
Implementation Method 2
or oxidized to form an OSL
Implementation Method 3
A multilayer stack comprised of a seed layer and an overlying (Co/Ni)X or (CoZFe(100-Z)/Ni)X multilayer that provides high PMA
Implementation Method 4
enhances the interface smoothness and spin-orbit interactions
Data Source
AI summary
Perpendicular magnetic anisotropy and Hc are enhanced in magnetic devices with a Ta/M1/M2 seed layer where M1 is preferably Ti, and M2 is preferably Cu, and including an overlying (Co/Ni)X multilayer (x is 5 to 50) that is deposited with ultra high Ar pressure of >100 sccm to minimize impinging energy that could damage (Co/Ni)X interfaces. In one embodiment, the seed layer is subjected to one or both of a low power plasma treatment and natural oxidation process to form a more uniform interface with the (Co/Ni)X multilayer. Furthermore, an oxygen surfactant layer may be formed at one or more interfaces between adjoining (Co/Ni)X layers in the multilayer stack. Annealing at temperatures between 180° C. and 400° C. also increases Hc but the upper limit depends on whether the magnetic device is MAMR, MRAM, a hard bias structure, or a perpendicular magnetic medium.