Magnetic Tunnel Junction Diffusion Stop Layer Oxygen Contamination
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Solution Overview
Problem
Existing magnetic tunnel junction (MTJ) fabrication techniques face challenges in controlling the oxidation process, leading to oxygen contamination of ferromagnetic layers, which degrades the performance by reducing tunneling magnetoresistance (TMR) values and breakdown voltage, especially in low-resistance-area (RA) MTJs.
Innovation Solution
Incorporating diffusion stop layers between the ferromagnetic and insulator barrier layers to prevent oxygen and nitrogen diffusion during oxidation and annealing processes, using metals like chromium, hafnium, and aluminum to form oxide or nitride layers that block contaminants, thereby maintaining the integrity of the ferromagnetic layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxidation process is performed to form insulator barrier layer, then barrier layer is formed, but oxygen diffuses into ferromagnetic layers causing contamination and performance degradation
Solution Approach 1:
A diffusion stop layer is introduced as an intermediary layer between the ferromagnetic layer and the insulator barrier layer. This intermediate layer selectively blocks oxygen diffusion from the barrier layer into the ferromagnetic layer while allowing the barrier layer to form properly through oxidation of the diffusion stop layer itself.
Solution Approach 2:
The diffusion stop layer is deposited on the ferromagnetic layer before the oxidation process that forms the insulator barrier layer. This preliminary placement of the diffusion stop layer prevents oxygen contamination before it can occur during the subsequent oxidation and annealing processes.
2Measurement precision
If barrier layer thickness is reduced to increase TMR, then tunneling magnetoresistance increases, but breakdown voltage decreases
Solution Approach 1:
The invention changes the chemical composition and structural parameters of the barrier layer by forming it as an oxide or nitride of the diffusion stop layer material. This allows optimization of barrier thickness and composition to achieve high TMR while the controlled oxidation process maintains structural integrity for adequate breakdown voltage.
3Reliability
If nitrogen is used to form nitride barrier layer, then barrier properties are improved, but nitrogen diffuses into ferromagnetic layers causing contamination
Solution Approach 1:
The diffusion stop layer serves as an intermediary that forms a nitride barrier layer with improved properties while the diffusion stop layer itself acts as a barrier preventing nitrogen from diffusing into the ferromagnetic layer, thus solving both the need for good barrier properties and the prevention of contamination.
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 ensures reliable and controllable oxidation, achieving high TMR values, designed RA values, and high intrinsic breakdown voltage, minimizing contamination and enhancing the performance of MTJs across large wafer sizes.
Implementation Method 1
when the thickness of the insulator is sufficiently thin, e.g., a few nanometers or less, electrons in the two ferromagnetic layers can 'penetrate' through the thin layer of the insulator due to a tunneling effect under a bias voltage applied to the two ferromagnetic layers across the barrier layer
Implementation Method 2
Incorporating diffusion stop layers between the ferromagnetic and insulator barrier layers to prevent oxygen and nitrogen diffusion during oxidation and annealing processes
Implementation Method 3
using metals like chromium, hafnium, and aluminum to form oxide or nitride layers that block contaminants
Implementation Method 4
using metals like chromium, hafnium, and aluminum to form oxide or nitride layers that block contaminants
Data Source
AI summary
Magnetic or magnetoresistive tunnel junctions (MTJs) having diffusion stop layers to eliminate or reduce diffusion of oxygen, nitrogen or other particles from the barrier layer to the ferromagnetic layers during the film deposition process including the barrier oxidation or nitridation process and the post annealing process. Such MTJs may be used in various applications including magnetic memory (MRAM) devices and magnetic recording heads.