Amorphous Insertion Layer for MTJ Exchange Coupling
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Solution Overview
Problem
Current Magnetic Tunneling Junction (MTJ) elements face challenges in achieving a high enough exchange coupling field (Hex) between the AFM and AP2 layers, leading to pinning dispersion and noise issues, which are not adequately addressed for ultra-high density recording heads.
Innovation Solution
Incorporating an amorphous insertion layer between the AFM and AP2 pinned layers or within the AP2 layer in the pinned layer stack, composed of elements like Co, Fe, Ni, B, Zr, Hf, Nb, Ta, Ti, and Si, to enhance the Hex/Hc ratio and reduce pinning dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional MTJ element structure is used without an amorphous insertion layer, then the device complexity is lower, but the exchange coupling field (Hex) between AFM and AP2 layers is insufficient leading to pinning dispersion
Solution Approach 1:
An amorphous insertion layer is introduced between the AFM layer and the AP2 pinned layer to mediate the exchange coupling interaction. This intermediary layer enhances the Hex/Hc ratio and reduces pinning dispersion, resolving the contradiction between maintaining structural simplicity and achieving sufficient exchange coupling field.
Solution Approach 2:
The pinned layer stack is constructed as a composite structure incorporating an amorphous insertion layer with specific composition (containing B, Si, or other elements) between crystalline AFM and AP2 layers. This composite approach optimizes magnetic properties while managing the increased structural complexity.
2Reliability
If the AFM and AP2 layers are directly coupled without an insertion layer, then the manufacturing process is simpler, but pinning dispersion and noise issues occur
Solution Approach 1:
The amorphous insertion layer serves as a mediator between AFM and AP2 layers, improving pinning stability and reducing noise through enhanced exchange coupling. While it adds a deposition step, the layer can be formed using standard sputtering techniques with controlled composition to manage manufacturing complexity.
Solution Approach 2:
The insertion layer's composition parameters (containing B, Si, or other elements at controlled concentrations) are optimized to achieve the desired Hex/Hc ratio improvement. By controlling the insertion layer thickness and composition, the patent balances manufacturing ease with improved pinning stability.
3Reliability
If a thicker insertion layer is used to improve Hex, then the exchange coupling field increases, but the layer thickness increases adding to device complexity
Solution Approach 1:
The patent optimizes the insertion layer thickness parameter to achieve sufficient Hex enhancement without excessive thickness. The amorphous layer with specific composition (containing B, Si, or other elements) is deposited at controlled thickness to balance exchange coupling improvement with minimal impact on overall device dimensions and complexity.
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 amorphous insertion layer increases the Hex/Hc ratio, reducing pinning dispersion and noise, thereby improving the performance and stability of MTJ elements for high-density recording applications.
Implementation Method 1
a bottom synthetic spin valve film stack is employed for biasing reasons and a CoFe/NiFe composite free layer is conventionally used following the tradition of CIP-GMR technology. GMR spin valve stacks are known to have a configuration in which two ferromagnetic layers are separated by a non-magnetic conductive layer (spacer). One type of CPP-GMR sensor is called a metallic CPP-GMR that can be represented by the following configuration in which the spacer is a copper layer: Seed/AFM/AP2/Ru/AP1/Cu/free layer/capping layer.
Implementation Method 2
The thin tunnel barrier layer above the pinned layer is so thin that a current through it can be established by quantum mechanical tunneling of conduction electrons.
Implementation Method 3
All layers in the MTJ element are preferably formed in a sputter deposition system that includes one or more sputter deposition chambers and at least one oxidation chamber.
Implementation Method 4
a conventional deposition system including a sputter deposition system and an oxidation chamber
Data Source
AI summary
An insertion layer is provided between an AFM layer and an AP2 pinned layer in a GMR or TMR element to improve exchange coupling properties by increasing Hex and the Hex/Hc ratio without degrading the MR ratio. The insertion layer may be a 1 to 15 Angstrom thick amorphous magnetic layer comprised of at least one element of Co, Fe, or Ni, and at least one element having an amorphous character selected from B, Zr, Hf, Nb, Ta, Si, or P, or a 1 to 5 Angstrom thick non-magnetic layer comprised of Cu, Ru, Mn, Hf, or Cr. Preferably, the content of the one or more amorphous elements in the amorphous magnetic layer is less than 40 atomic %. Optionally, the insertion layer may be formed within the AP2 pinned layer. Examples of an insertion layer are CoFeB, CoFeZr, CoFeNb, CoFeHf, CoFeNiZr, CoFeNiHf, and CoFeNiNbZr.