CoFeB Storage Element with Laminated Ferri-Pinned Layer for Thermal Stability
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Solution Overview
Problem
STT-MRAM storage elements face challenges in achieving thermal stability while reducing element size and increasing capacity, as miniaturization tends to decrease thermal stability and requires lower reversal currents to prevent dielectric breakdown.
Innovation Solution
A storage element with a layered construction using a perpendicular magnetization storage layer, a laminated ferri-pinned pinned magnetization layer, and a CoFeB magnetic layer, where the Pt group metal element's atomic concentration is lower than the ferromagnetic 3d transition metal element's, enhancing laminated ferri coupling strength and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the element size is reduced to increase storage capacity, then storage capacity increases, but thermal stability deteriorates
Solution Approach 1:
The patent changes the magnetic anisotropy parameter from in-plane to perpendicular magnetization by modifying the storage layer composition (using CoFeB with specific thickness ratios of Co and Fe layers). This parameter change enables thermal stability to be maintained even as element size is reduced for increased storage capacity.
Solution Approach 2:
The patent employs composite material structures including CoFeB alloy layers with specific compositional ratios, combined with pinned layers and insulating layers. The CoFeB layer uses a composite structure of Co and Fe atoms in controlled ratios to achieve both perpendicular magnetization and thermal stability in miniaturized elements.
2Quantity of substance
If the element size is reduced to increase storage capacity, then storage capacity increases, but reversal current decreases leading to dielectric breakdown
Solution Approach 1:
The patent changes the magnetization direction to perpendicular, which fundamentally alters the spin torque reversal mechanism. This parameter change allows for lower reversal current densities that do not cause dielectric breakdown, enabling safe miniaturization for increased storage capacity.
Solution Approach 2:
The patent applies different material compositions and structures to specific layers: the storage layer uses CoFeB with optimized thickness ratios for perpendicular magnetization, while pinned layers use different compositions. This local quality differentiation enables the storage layer to achieve low reversal current without compromising the overall device reliability.
3Ease of manufacture
If conventional in-plane magnetization is used, then device construction is simple, but thermal stability is insufficient for miniaturized elements
Solution Approach 1:
The patent changes the magnetic anisotropy parameter from in-plane to perpendicular by modifying the storage layer composition and structure. This parameter change maintains ease of manufacture through sputtering deposition while achieving the thermal stability required for miniaturized elements.
Solution Approach 2:
The patent utilizes thermal processing (heat treatment at 200-400°C) to stabilize the perpendicular magnetization and enhance thermal stability. This thermal processing step, applied after deposition, locks in the desired magnetic properties and ensures stability for miniaturized elements.
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 improves thermal stability, allows for further miniaturization, and increases storage capacity while reducing power consumption and operation errors, resulting in a highly reliable magnetic head with superior thermal stability.
Implementation Method 1
recording of information in the storage layer is carried out by changing the direction of magnetization of the storage layer by injecting spin-polarized electrons
Implementation Method 2
a pinned magnetization layer that has magnetization perpendicular to a surface of the pinned magnetization layer and serves as a standard for information stored in the storage layer
Implementation Method 3
the pinned magnetization layer has a laminated ferri-pinned construction composed of at least two ferromagnetic layers and a non-magnetic layer
Data Source
AI summary
A storage element is provided. The storage element includes a memory layer; a fixed magnetization layer; an intermediate layer including a non-magnetic material; wherein the intermediate layer is provided between the memory layer and the fixed magnetization layer; wherein the fixed magnetization layer includes at least a first magnetic layer, a second magnetic layer, and a non-magnetic layer, and wherein the first magnetic layer includes a CoFeB composition. A memory apparatus and a magnetic head are also provided.