Non-ferromagnetic Spacing Composite Layer for MRAM Thermal Stability
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Solution Overview
Problem
The thermal stability of magnetoresistive random access memory (MRAM) elements with synthetic antiferromagnetic laminated structures is compromised due to high temperature thermal treatments, leading to a sudden drop in coupling strength and loss of RKKY indirect interaction, which affects the magnetic properties and recording function.
Innovation Solution
A non-ferromagnetic spacing composite layer with a specific multilayer structure, comprising a first and third spacing layer of materials like rhenium, iridium, or tungsten, and a second spacing layer of ruthenium, is introduced to maintain coupling strength and RKKY indirect interaction even after high temperature thermal treatments, ensuring the MRAM element's thermal durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple non-ferromagnetic layer is used in the synthetic antiferromagnetic structure, then the device complexity is reduced, but the thermal stability deteriorates due to coupling strength drop after high temperature treatment
Solution Approach 1:
The patent applies composite materials by using a multilayer non-ferromagnetic spacing layer structure comprising alternating layers of first non-ferromagnetic material (e.g., Ru, Rh, Ir, Pt, Pd) and second non-ferromagnetic material (e.g., Ta, W, Mo, Hf, Nb). This composite structure maintains coupling strength after high temperature thermal treatments while managing thermal expansion differences, thereby improving thermal stability without excessive complexity
Solution Approach 2:
The patent segments the single non-ferromagnetic layer into multiple alternating layers of different materials. The non-ferromagnetic spacing layer is divided into a stack of thin layers with each layer being 0.1-0.5 nm thick, creating a segmented structure that prevents coupling strength drop during thermal treatment while keeping individual layer complexities low
2Volume of moving object
If the non-ferromagnetic layer thickness is reduced to maintain total thickness within 0.5-1.5 nm, then the device miniaturization is achieved, but the coupling strength suddenly drops after thermal treatment
Solution Approach 1:
The patent uses composite materials with alternating layers of different non-ferromagnetic materials where each thin layer (0.1-0.5 nm) contributes to maintaining coupling strength. The combination of materials with different thermal expansion coefficients creates a composite structure that preserves RKKY interaction after thermal treatment despite the total thickness being within 0.5-1.5 nm
Solution Approach 2:
The patent changes the material composition parameters by selecting specific non-ferromagnetic materials with appropriate thermal expansion coefficients and atomic spacing. By adjusting the material types and their alternating sequence, the coupling strength is maintained after thermal treatment while keeping the total thickness within the required 0.5-1.5 nm range
3Ease of manufacture
If high temperature thermal treatment is applied to complete back-end processes, then the manufacturing process compatibility is improved, but the RKKY indirect interaction is lost due to coupling strength drop
Solution Approach 1:
The patent employs composite materials with alternating layers of non-ferromagnetic materials that have different thermal expansion coefficients. This composite structure allows the synthetic antiferromagnetic layer to withstand high temperature thermal treatments (400-500°C) required for back-end CMOS processes while maintaining coupling strength and preserving RKKY indirect interaction
Solution Approach 2:
The patent applies beforehand cushioning by designing a multilayer non-ferromagnetic spacing structure with materials selected for their thermal stability characteristics. This pre-engineered structure cushions against the harmful effects of high temperature thermal treatment, preventing coupling strength drop and maintaining magnetic properties throughout the manufacturing process
4Device complexity
If thermal expansion coefficient mismatch between non-ferromagnetic and ferromagnetic layers is not considered, then the material selection is simplified, but the coupling strength drops suddenly after thermal treatment
Solution Approach 1:
The patent applies composite materials by alternating layers of non-ferromagnetic materials with different thermal expansion coefficients. This composite structure compensates for thermal expansion mismatch between the non-ferromagnetic and ferromagnetic layers during high temperature treatment, maintaining coupling strength without requiring complex material design
Solution Approach 2:
The patent applies local quality by assigning different material properties to different layers within the non-ferromagnetic spacing structure. Each alternating layer has specific thermal expansion characteristics tailored to compensate for local stress and maintain coupling strength, while the overall structure remains relatively simple
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 proposed solution maintains coupling strength and RKKY indirect interaction after thermal treatments, preventing damage to the magnetic properties and ensuring the recording function of MRAM elements, thus facilitating their integration into semiconductor manufacturing processes.
Implementation Method 1
maintain coupling strength and RKKY indirect interaction even after high temperature thermal treatments
Implementation Method 2
STT is accomplished by the magnetic tunnel junction (MTJ) involving the tunneling magnetoresistance (TMR) effect
Implementation Method 3
The spin directions of the tunneling or polarized electrons can be maintained. Unlike the fixed magnetization direction of the reference layer, the magnetization direction of the free layer can be switched with STT effect by micro-current injection
Implementation Method 4
GMR effect is observed in a laminate composed of ferromagnetic layer/non-ferromagnetic layer/ferromagnetic layer as electrons with different spin orientations tunneling the ferromagnetic layers have different electron conductivities. The electrical resistance depends on an external magnetic field
Data Source
AI summary
Provided is a non-ferromagnetic spacing composite layer, comprising first, second and third spacing layers stacked in sequence. The first and third spacing layers are each made of Re, Rh, Ir, W, Mo, Ta, or Nb, and the second spacing layer is made of Ru. The second spacing layer has a thickness of equal to or more than 0.18 nm, and the non-ferromagnetic spacing composite layer has a total thickness of 0.6 nm to 1 nm. Also, provided are a method of preparing the non-ferromagnetic spacing composite layer, a synthetic antiferromagnetic laminated structure, and an MRAM. The synthetic antiferromagnetic laminated structure can maintain a certain coupling strength and the RKKY indirect interaction after thermal treatment, thereby keeping the recording function of MRAM.