Amorphous Blocking Layers in Bottom-Type pMTJ Elements
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Solution Overview
Problem
The existing bottom-type perpendicular magnetic tunnel junction (pMTJ) elements in STT-MRAM cells face challenges in achieving high perpendicular magnetic anisotropy (PMA) and tunnel magnetoresistance (TMR) due to mismatches and diffusions at interfaces of different polycrystalline structures and textures, which hinder effective write and read operations.
Innovation Solution
Incorporating thermally stable amorphous blocking layers, with a first amorphous nonmagnetic film blocking a body-center-cubic (bcc) texture to allow fcc texture growth for the keeper and lower reference layers, and a second amorphous ferromagnetic film blocking to enable bcc texture growth for the upper reference and storage layers, thereby eliminating interface mismatches and diffusions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polycrystalline structures and textures are used in pMTJ elements to achieve high perpendicular magnetic anisotropy (PMA), then write operation performance is improved, but interface mismatches and diffusions occur between layers with different structures, deteriorating PMA and tunnel magnetoresistance (TMR)
Solution Approach 1:
An amorphous blocking layer is introduced as an intermediary between the diffusion barrier layer and the ferromagnetic layers. This amorphous layer acts as a mediator that prevents the transmission of bcc texture from the diffusion barrier layer to the keeper and reference layers, thereby eliminating interface mismatches and diffusions while allowing the ferromagnetic layers to maintain their desired polycrystalline structures and high PMA
Solution Approach 2:
The patent changes the structural parameter of the blocking layer from polycrystalline to amorphous. This parameter change eliminates the texture mismatch issue because amorphous materials do not have crystalline orientation, thus preventing the transmission of unwanted bcc texture and interface diffusions while maintaining thermal stability
2Strength
If polycrystalline structures with specific textures are used in barrier and storage layers to achieve high tunnel magnetoresistance (TMR), then read operation performance is improved, but interface mismatches with buffer layers occur, deteriorating TMR
Solution Approach 1:
The amorphous blocking layer serves as an intermediary that decouples the interface between the buffer layer and the upper reference/barrier/storage layers. It prevents the transmission of incompatible textures from the buffer layer to the TMR-active layers, allowing these layers to develop their optimal polycrystalline structures and textures for high TMR without interface mismatch constraints
3Strength
If high temperature annealing is performed to enhance magnetic properties, then PMA and TMR are improved, but thermal diffusion occurs at interfaces of different polycrystalline structures, further deteriorating magnetic properties
Solution Approach 1:
The amorphous blocking layer acts as a thermal diffusion barrier during high temperature annealing processes. Its amorphous structure and chemical composition create a stable interface that prevents thermal diffusion between layers with different polycrystalline structures, allowing high temperature annealing to be performed to enhance PMA and TMR without causing interface deterioration
Solution Approach 2:
The patent utilizes the thermal stability parameter of amorphous materials to resist crystallization and maintain structural integrity during high temperature annealing. This parameter change enables the blocking layer to remain amorphous during thermal processing, preventing interface diffusions while allowing the desired magnetic properties to be developed
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 development of strong perpendicular magnetic anisotropy and high tunnel magnetoresistance, enhancing the performance of pMTJ elements in both write and read operations by maintaining desired magnetic properties and resistance ratios.
Implementation Method 1
blocks a polycrystalline diffusion barrier layer with a body-center-cubic (bcc) texture in order for the keeper and lower reference layers of the bottom-type pMTJ element to freely grow with a face-centered-cubic (fcc) texture, thereby developing strong perpendicular magnetic anisotropy (PMA)
Implementation Method 2
blocks the keeper and lower reference layers of the bottom-type pMTJ element in order for the upper reference, barrier and storage layers of the bottom-type pMTJ element to freely grow with a bcc texture, thereby exhibiting a strong tunneling magnetoresistance (TMR) effect
Implementation Method 3
Mismatches at interfaces of different polycrystalline structures and textures may cause difficulties in attaining the desired high PMA and ΔRT/RO. Furthermore, after annealing at high temperatures, diffusions may occur at interfaces of different polycrystalline structures and textures and thus further deteriorate the PMA and ΔRT/RO
Data Source
AI summary
The invention provides a bottom-type perpendicular magnetic tunnel junction (pMTJ) element with thermally stable amorphous blocking layers for high-density nonvolatile data storage. The first blocking layer, preferably formed of an amorphous nonmagnetic film, blocks a polycrystalline diffusion barrier layer with a body-center-cubic (bcc) <110> texture in order for the keeper and lower reference layers of the bottom-type pMTJ element to freely grow with a face-centered-cubic (fcc) <111> texture, thereby developing strong perpendicular magnetic anisotropy (PMA). The second blocking layer, preferably formed of an amorphous ferromagnetic film, blocks the keeper and lower reference layers of the bottom-type pMTJ element in order for the upper reference, barrier and storage layers of the bottom-type pMTJ element to freely grow with a <001> texture, thereby exhibiting a strong tunneling magnetoresistance (TMR) effect.