Thin Composite Seed Layer for Perpendicular Magnetic Anisotropy Stabilization
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Solution Overview
Problem
Current magnetic recording technologies face challenges in achieving high perpendicular magnetic anisotropy (PMA) in hard bias structures for spin valve sensors, particularly at high recording densities, due to the need for thick seed layers that are impractical and often require high-temperature annealing, which can damage device components.
Innovation Solution
A thin composite seed layer with a Ta/M1/M2 configuration, where M1 is Ru or other metals with fcc(111) crystal orientation, is used to enhance the (111) texture in a laminated Co/Ni hard bias layer, allowing for high PMA without heat treatment, and preserving the Co/Ni interfaces to maintain magnetic anisotropy, thereby stabilizing the free layer in spin valve sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick seed layer is used to establish perpendicular magnetic anisotropy in the hard bias layer, then PMA can be achieved, but the device thickness increases and space restrictions are violated
Solution Approach 1:
The patent employs a composite seed layer structure comprising multiple materials (Ta, Ru, Rh, Ir, or Os in various combinations) rather than a single thick seed layer. This composite approach enables the establishment of perpendicular magnetic anisotropy in the overlying Co/Ni hard bias layer while maintaining a thin overall seed layer thickness, thus resolving the contradiction between achieving sufficient PMA and minimizing device thickness.
2Length of stationary object
If the seed layer is made thin to satisfy space restrictions, then device compactness is improved, but PMA establishment becomes insufficient
Solution Approach 1:
By using composite seed layer configurations such as Ta/Ru, Ta/Rh, Ta/Ir, or Ta/Os with optimized thicknesses, the patent achieves sufficient perpendicular magnetic anisotropy in the hard bias layer even with thin seed layers. The specific combination of materials with different magnetic and structural properties enables effective PMA establishment within space constraints.
Solution Approach 2:
The patent optimizes the thickness parameters of individual seed layer components (e.g., Ta layer 5-50 nm, Ru layer 5-20 nm, Rh layer 5-15 nm, Ir layer 5-10 nm, Os layer 5-10 nm) to achieve the desired balance between thin overall thickness and sufficient PMA establishment. By carefully adjusting these parameters, the system maintains compact dimensions while ensuring adequate magnetic anisotropy.
3Strength
If heat treatment is applied to enhance PMA, then magnetic anisotropy is improved, but the manufacturing process complexity increases
Solution Approach 1:
The composite seed layer structure is designed to inherently provide the necessary perpendicular magnetic anisotropy through its material composition and interface structure, eliminating the need for additional heat treatment processes. The system self-establishes the required magnetic properties during the standard deposition process, thereby simplifying the manufacturing workflow while maintaining high PMA.
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 enables the achievement of high coercivity and squareness in the hard bias layer with a thinner seed layer, maintaining PMA and biasing efficiency even at reduced thicknesses, ensuring stable domain states and minimizing noise in high-density recording systems.
Implementation Method 1
A thin composite seed layer with a Ta/M1/M2 configuration, where M1 is Ru or other metals with fcc(111) crystal orientation, is used to enhance the (111) texture in an overlying laminated Co/Ni hard bias layer
Implementation Method 2
A thin composite seed layer with a Ta/M1/M2 configuration, where M1 is Ru or other metals with fcc(111) crystal orientation, is used to enhance the (111) texture in an overlying laminated Co/Ni hard bias layer, allowing for high PMA without the need for heat treatment
Implementation Method 3
The solution achieves high coercivity and squareness in the hard bias layer, with Hk over 15000 Oe and Mrt values higher than CoPt, while preserving the Co/Ni interfaces to stabilize the free layer in spin valve structures, ensuring efficient longitudinal biasing
Data Source
AI summary
A hard bias (HB) structure for producing longitudinal bias to stabilize a free layer in an adjacent spin valve is disclosed and includes a composite seed layer made of at least Ta and a metal layer having a fcc(111) or hcp(001) texture to enhance perpendicular magnetic anisotropy (PMA) in an overlying (Co/Ni)x laminated layer. The (Co/Ni)x HB layer deposition involves low power and high Ar pressure to avoid damaging Co/Ni interfaces and thereby preserves PMA. A capping layer is formed on the HB layer to protect against etchants in subsequent process steps. After initialization, magnetization direction in the HB layer is perpendicular to the sidewalls of the spin valve and generates an Mrt value that is greater than from an equivalent thickness of CoPt. A non-magnetic metal separation layer may be formed on the capping layer and spin valve to provide an electrical connection between top and bottom shields.