MTJ Free-Layer Oxide Structure for Stable PMA and Fast Switching
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Solution Overview
Problem
Magnetic tunneling junction devices face challenges in achieving fast operating speeds and stable perpendicular magnetic anisotropy, which are crucial for improving the performance of magnetic memory devices like STT-MRAM.
Innovation Solution
The implementation of a magnetic tunneling junction device structure that includes a free layer doped with a non-magnetic metal, a first oxide layer with a stoichiometrically oxygen-deficient composition, and a second oxide layer with a metal oxide having a higher oxygen affinity than the non-magnetic metal, which enhances interface perpendicular magnetic anisotropy and prevents oxygen interdiffusion, thereby stabilizing the magnetic properties and increasing operating speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a magnetic tunneling junction device uses conventional structures, then it achieves basic memory functionality, but the operating speed is limited to 50-100 nsec and perpendicular magnetic anisotropy stability is insufficient
Solution Approach 1:
The patent introduces a second oxide layer with specific metal oxide composition at the interface with the free layer, creating localized regions with enhanced perpendicular magnetic anisotropy. This local modification at the interface enables stable PMA without compromising the overall device structure, achieving both fast switching speeds and reliable magnetic stability
Solution Approach 2:
The patent employs a composite structure combining magnetic materials (CoFeB, CoFe) with specific oxide materials (MgO, Al2O3, TiO2, Ta2O5) in layered configurations. This composite approach allows optimization of both spin transport properties for fast switching and interface anisotropy for stability, resolving the contradiction between speed and reliability
2Productivity
If the free layer uses magnetic materials with high spin polarization, then switching efficiency improves, but oxygen interdiffusion at interfaces degrades the magnetic properties and stabilizes the anisotropy
Solution Approach 1:
The patent introduces oxide layers (MgO, Al2O3, TiO2, Ta2O5) as intermediary barrier layers between the magnetic free layer and adjacent layers. These intermediary oxide layers prevent direct oxygen interdiffusion while maintaining spin transport efficiency, thus preserving both switching performance and interface compositional stability
Solution Approach 2:
The patent uses oxide materials with low oxygen mobility and high chemical stability (such as Al2O3 and Ta2O5) to create an inert interface environment that resists oxygen diffusion. This inert barrier approach protects the magnetic free layer from degradation while maintaining high switching efficiency
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 configuration results in improved operating speeds of less than 10 nsec and maintains stable perpendicular magnetic anisotropy, enhancing the performance and reliability of magnetic memory devices.
Implementation Method 1
a second oxide layer on the second surface of the free layer... an oxygen affinity of a metal in the metal oxide of the second oxide layer is greater than an oxygen affinity of the non-magnetic metal of the free layer
Implementation Method 2
The resistance of the magnetic tunneling junction device varies with the magnetization direction of a free layer. For example, when the magnetization direction of the free layer is the same as the magnetization direction of a pinned layer, the magnetic tunneling junction device may have low resistance, and when the magnetization directions are opposite to each other, the magnetic tunneling junction device may have high resistance
Implementation Method 3
Spin Transfer Torque-Magnetic RAM (STT-MRAM) that is currently mass-produced may have an operating speed of about 50 to 100 nsec
Data Source
AI summary
Provided are a magnetic tunneling junction device having more stable perpendicular magnetic anisotropy (PMA) and/or increased operating speed, and/or a memory device including the magnetic tunneling junction device. The magnetic tunneling junction device includes a free layer having a first surface and a second surface opposite the first surface; a pinned layer facing the first surface of the free layer; a first oxide layer between the pinned layer and the free layer; and a second oxide layer on the second surface of the free layer. The free layer includes a magnetic material X doped with a non-magnetic metal. The second oxide layer includes ZOx which is an oxide of a metal Z. An oxygen affinity of the metal Z is greater than an oxygen affinity of the non-magnetic metal X.