Amorphous Diffusion Barrier for MRAM Thermal Stability
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Solution Overview
Problem
Magnetoresistance film stacks in magnetic heads and MRAMs face deterioration of characteristics and reduced MR ratios due to manganese diffusion during high-temperature heat treatment processes, leading to instability and increased manufacturing costs.
Innovation Solution
Incorporating an amorphous diffusion suppressing layer with a composition of X—Y—Z, where X represents Co, Fe, or Ni, and Y and Z include elements like Al, Si, Ta, Nb, Zr, Hf, W, Mo, Ti, and V, and N, C, or B, respectively, to prevent manganese diffusion through grain boundaries, and using a sputtering method with controlled pressure to form a stable amorphous structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-temperature heat treatment is applied to manufacture magnetoresistance elements, then manufacturing process completion is achieved, but manganese diffusion occurs causing deterioration of characteristics and reduced MR ratios
Solution Approach 1:
An amorphous diffusion suppressing layer is introduced as an intermediary between the antiferromagnetic layer and the fixed ferromagnetic layer. This layer acts as a barrier that prevents manganese atoms from diffusing through grain boundaries during high-temperature heat treatment, thereby maintaining the magnetoresistance characteristics while allowing the manufacturing process to proceed.
Solution Approach 2:
The invention uses a composite structure consisting of multiple layers with different functions: the amorphous diffusion suppressing layer (made of materials like Co-Al-N, Fe-Si-B, or Ni-Al-B) combined with the fixed ferromagnetic layer. This composite structure provides both the necessary magnetic properties and diffusion barrier functionality simultaneously.
2Device complexity
If conventional film stacks are used without diffusion suppressing layers, then device structure is simple, but manganese diffusion through grain boundaries causes characteristic deterioration
Solution Approach 1:
The amorphous diffusion suppressing layer serves as a mediator that blocks the diffusion path of manganese atoms through grain boundaries. Although this adds a layer to the structure, it is thin (1-5 nm) and can be deposited in the same vacuum chamber as other layers, minimizing the practical increase in device complexity while significantly improving manufacturing precision.
3Ease of manufacture
If heat treatment at 350°C or higher is conducted, then element manufacturing is completed, but interdiffusion of film stack elements occurs decreasing MR ratio
Solution Approach 1:
The amorphous diffusion suppressing layer acts as a protective intermediary that prevents interdiffusion of elements between the film stack layers during high-temperature heat treatment. The amorphous structure lacks grain boundaries, providing a continuous barrier that maintains the magnetoresistance change ratio even after heat treatment at 350°C or higher.
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 effectively prevents manganese diffusion and maintains high MR ratios even after heat treatment at 350°C, enhancing the manufacturing yield and reducing costs while ensuring thermal stability and low specific resistance.
Implementation Method 1
prevent manganese diffusion through grain boundaries
Implementation Method 2
Incorporating an amorphous diffusion suppressing layer with a composition of X—Y—Z
Implementation Method 3
using a sputtering method with controlled pressure to form a stable amorphous structure
Implementation Method 4
The magnetoresistance effect is a phenomenon that a film stack including the structure of a ferromagnetic layer, a nonmagnetic layer and another ferromagnetic layer exhibits a change in the resistance depending on the relative angle between the magnetization directions
Implementation Method 5
laminate a magnetic film that functions as the fixed magnetic layer with an antiferromagnetic layer, so that magnetization of the fixed magnetic layer is fixed by an exchange coupling magnetic field generated across the interface between these films
Data Source
AI summary
A magnetoresistance element includes an antiferromagnetic layer, a fixed ferromagnetic layer, a first nonmagnetic layer and a free ferromagnetic layer. The antiferromagnetic layer is formed on the upper surface side of a substrate. The fixed ferromagnetic layer is formed on the antiferromagnetic layer. The first nonmagnetic layer is formed on the fixed ferromagnetic layer. The free ferromagnetic layer is formed on the first nonmagnetic layer. The fixed ferromagnetic layer is provided with an amorphous layer. The amorphous layer contains amorphous material having a composition expressed by a chemical formula of X—Y—N. X is an element selected from Co, Fe and Ni. Y is an element selected from AI, Si, Mg, Ta, Nb, Zr, Hf, W, Mo, Ti and V. N represents nitrogen.