Multilayered Seed Structure for Perpendicular MTJ Memory
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Solution Overview
Problem
Spin transfer torque magnetic random access memory (STT-MRAM) devices face challenges in achieving a high tunnel magnetoresistance (TMR) ratio and cost-effective manufacturing, particularly as the size of the magnetic tunnel junctions is miniaturized, leading to broader resistance distribution and increased power consumption.
Innovation Solution
The implementation of a multilayered seed structure formed by interleaving sublayers, such as CoFeB and Ta, to create a unit bilayer structure that provides a smooth surface for magnetic layers, enhancing the TMR ratio and reducing power consumption while maintaining scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the size of the perpendicular MTJ is reduced for scalability, then power consumption is reduced, but the resistance distribution becomes broader and TMR ratio decreases
Solution Approach 1:
The patent changes the structural parameters of the seed layer from a conventional single-layer configuration to a multilayered structure with alternating ferromagnetic and nonmagnetic sublayers. This parameter change in the seed layer structure improves the TMR ratio by enhancing perpendicular magnetic anisotropy and magnetization alignment, thereby resolving the degradation of TMR ratio that occurs with MTJ miniaturization while maintaining reduced power consumption
Solution Approach 2:
The patent employs a composite multilayered seed structure combining different materials (ferromagnetic elements such as Co, Fe, Ni with nonmagnetic elements such as Ru, Rh, Ir, Ta, W) in alternating sublayers. This composite structure provides both the necessary perpendicular magnetic anisotropy for high TMR ratio and the structural stability required for miniaturized devices, thus resolving the contradiction between maintaining high TMR ratio and achieving scalability
2Use of energy by moving object
If the size of the perpendicular MTJ is reduced for scalability, then power consumption is reduced, but the resistance distribution becomes broader
Solution Approach 1:
The patent modifies the seed layer parameters by creating a multilayered structure with controlled thicknesses of ferromagnetic and nonmagnetic sublayers. This parameter optimization ensures uniform magnetization switching characteristics across the MTJ population, narrowing the resistance distribution even as device size is reduced, thereby maintaining manufacturing precision while achieving lower power consumption
Solution Approach 2:
The patent introduces local quality variations in the seed layer by using alternating ferromagnetic and nonmagnetic sublayers with different magnetic properties. This local differentiation in magnetic characteristics ensures uniform perpendicular magnetization alignment across the entire MTJ structure, reducing resistance distribution variability and enabling reliable miniaturization with controlled power consumption
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 multilayered seed structure improves the TMR ratio and reduces power consumption by providing a stable and efficient switching mechanism for magnetic memory elements, addressing the challenges of miniaturization and manufacturing costs in STT-MRAM devices.
Implementation Method 1
The implementation of a multilayered seed structure formed by interleaving sublayers, such as CoFeB and Ta, to create a unit bilayer structure that provides a smooth surface for magnetic layers
Implementation Method 2
Spin transfer torque magnetic random access memory (STT-MRAM) is a new class of non-volatile memory
Implementation Method 3
The magnetic reference layer 50 and free layer 52 have magnetization directions 58 and 60, respectively, which are substantially perpendicular to the respective layer planes. Therefore, the MTJ 56 is a perpendicular type comprising the magnetic layers 50 and 52 with perpendicular anisotropy
Implementation Method 4
When the magnetization directions 60 and 58 of the magnetic free layer 52 and reference layer 50 are substantially parallel, electrons polarized by the magnetic reference layer 50 can tunnel through the insulating tunnel junction layer 54, thereby decreasing the electrical resistance of the perpendicular MTJ 56
Data Source
AI summary
The present invention is directed to a magnetic random access memory element that includes a multilayered seed structure formed by interleaving multiple layers of a first transition metal with multiple layers of a second transition metal; and a first magnetic layer formed on top of the multilayered seed structure. The first magnetic layer has a multilayer structure formed by interleaving layers of the first transition metal with layers of a magnetic material and has a first fixed magnetization direction substantially perpendicular to a layer plane thereof. The first transition metal is platinum or palladium, while the second transition metal is selected from the group consisting of tantalum, titanium, zirconium, hafnium, vanadium, niobium, chromium, molybdenum, and tungsten.