Amorphous Buffer Layers in Magnetic Tunnel Junctions
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Solution Overview
Problem
Magnetic tunnel junction devices face issues with non-uniformity of the tunnel insulating layer during heat treatment, leading to deteriorated flatness and contamination, which affects the uniformity of magnetoresistance and increases the possibility of defective memory cells due to the use of multiple buffer layers and limitations in perpendicular magnetic anisotropy control.
Innovation Solution
A magnetic tunnel junction device is designed with a pinned layer incorporating an amorphous metal layer and a perpendicular magnetic anisotropy material layer, where the amorphous or nanocrystal material acts as a buffer, maintaining an amorphous state during heat treatment to prevent diffusion and ensure uniformity, and a thin FeZr layer is used to facilitate perpendicular magnetic anisotropy without the need for multiple buffer layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment process is applied to crystallize the tunnel insulating layer and ferromagnetic materials, then the characteristics of magnetic materials are improved, but the lower structure becomes rough and the flatness of the tunnel insulating layer deteriorates
Solution Approach 1:
An amorphous buffer layer is formed preliminarily on the lower structure before forming the tunnel insulating layer. This buffer layer is specifically designed to maintain its amorphous state during heat treatment, preventing the lower structure roughness from transferring to the tunnel insulating layer, thus preserving flatness while allowing magnetic material crystallization
Solution Approach 2:
The amorphous buffer layer acts as an intermediary between the lower structure and the tunnel insulating layer. It decouples the heat treatment effects, allowing the lower structure to crystallize and improve magnetic characteristics while the buffer layer remains amorphous and maintains a flat interface for the tunnel insulating layer
2Reliability
If heat treatment process is applied, then magnetic material characteristics are improved, but Mn particles diffuse toward the tunnel insulating layer and contaminate it
Solution Approach 1:
The amorphous buffer layer serves as a diffusion barrier and intermediary between the antiferromagnetic layer and the tunnel insulating layer. During heat treatment, it prevents Mn particles from diffusing into the tunnel insulating layer while still allowing the necessary magnetic material crystallization to occur
Solution Approach 2:
The harmful diffusion effect is extracted and isolated by introducing the amorphous buffer layer that specifically blocks Mn particle migration while permitting beneficial magnetic material transformations
3Reliability
If multiple buffer layers are used to control perpendicular magnetic anisotropy, then desired magnetic properties are achieved, but the fabrication process becomes complex and defective cells increase
Solution Approach 1:
Multiple buffer layers are merged into a single amorphous buffer layer that performs all necessary functions: controlling perpendicular magnetic anisotropy, maintaining flatness, preventing contamination, and enabling heat treatment. This simplification reduces fabrication complexity and defective cells while achieving the same magnetic properties
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 the uniformity of magnetoresistance, prevents antiferromagnetic particle diffusion, and allows for the realization of desired perpendicular magnetic anisotropy regardless of the crystal texture, reducing the risk of defective memory cells and simplifying the fabrication process.
Implementation Method 1
the amorphous or nanocrystal material acts as a buffer, maintaining an amorphous state during heat treatment to prevent diffusion
Implementation Method 2
magnetic tunnel junction (MTJ) device using a tunneling magnetoresistance (TMR) structure recently has received more attention
Implementation Method 3
a pinned layer having an amorphous metal layer, and a micro magnetic device using a perpendicular magnetic anisotropy material
Data Source
AI summary
According to a first embodiment of the present invention, a magnetic tunnel junction device comprises: a free layer having a magnetization in a variable direction; a pinned layer having a magnetization in a pinned direction; and a tunnel insulation film formed between the free layer and the pinned layer, wherein the pinned layer includes a ferromagnetic film and an amorphous metal film. In addition, a magnetic device according to a second embodiment of the present invention comprises: an amorphous or nanocrystal material layer; and a perpendicular magnetic anisotropic material layer formed on the amorphous or nanocrystal material layer. The amorphous or nanocrystal material layer is a predefined amorphous material or nanocrystal material layer serving as a lower layer, and the perpendicular magnetic anisotropic material layer is formed on the amorphous or nanocrystal material layer.