MTJ Under Layer with Anisotropy Increasing Layer for Thermal Stability
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Solution Overview
Problem
Existing memory devices face challenges in achieving high perpendicular magnetic anisotropy and thermal stability, which are crucial for reliable data storage and operation, due to insufficient crystal orientation and magnetic anisotropy at the interface between the under layer and the free layer in Magnetic Tunnel Junction (MTJ) structures.
Innovation Solution
Incorporating a perpendicular magnetic anisotropy increasing layer with a face-centered cubic (FCC) crystal structure, such as TiN, ZrN, or HfN, below the under layer, which has a different crystal structure from the under layer, to enhance crystal orientation and increase perpendicular magnetic anisotropy, and using a buffer layer with a hexagonal close-packed (HCP) structure to facilitate crystal growth and improve thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional under layer structure is used in the MTJ device, then the device structure remains simple, but the perpendicular magnetic anisotropy and thermal stability are insufficient
Solution Approach 1:
The under layer structure is segmented into multiple functional layers: a buffer layer (e.g., MgO) with NaCl crystal structure, a perpendicular magnetic anisotropy increasing layer (e.g., CoFeB, CoFe) with specific crystal orientation, and optionally a capping layer. This segmentation allows each layer to perform its specific function optimally, achieving high thermal stability and perpendicular magnetic anisotropy while maintaining reasonable structural complexity
Solution Approach 2:
The patent employs composite material structures where the under layer combines materials with different crystal structures and magnetic properties. The buffer layer uses NaCl-structure MgO, the anisotropy increasing layer uses materials like CoFeB or CoFe with specific crystal orientations, creating a composite structure that achieves superior thermal stability and magnetic anisotropy compared to single-material layers
2Reliability
If the crystal orientation at the under layer interface is insufficient, then the manufacturing process remains simple, but the perpendicular magnetic anisotropy is low
Solution Approach 1:
The patent optimizes specific parameters of the under layer structure to achieve high perpendicular magnetic anisotropy. This includes controlling the thickness of the buffer layer (e.g., 2-5 nm MgO), the thickness and composition of the anisotropy increasing layer, and the crystal orientation (e.g., (001) orientation). By precisely controlling these parameters, the patent achieves high perpendicular magnetic anisotropy while maintaining manufacturability
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 significantly improves the perpendicular magnetic anisotropy and thermal stability of the free layer, leading to enhanced data storage characteristics and operating performance of the variable resistance element, including increased thermal stability and improved switching properties.
Implementation Method 1
a perpendicular magnetic anisotropy increasing layer disposed below the under layer and including a material having a different crystal structure from the under layer
Implementation Method 2
a buffer layer disposed below the perpendicular magnetic anisotropy increasing layer and operating to facilitate crystal growth of the layers disposed over the buffer layer
Data Source
AI summary
An electronic device may include a semiconductor memory, and the semiconductor memory may include an MTJ (Magnetic Tunnel Junction) structure including a free layer having a variable magnetization direction, a pinned layer having a fixed magnetization direction, and a tunnel barrier layer interposed between the free layer and the pinned layer; an under layer disposed under the MTJ structure; and a perpendicular magnetic anisotropy increasing layer disposed below the under layer and including a material having a different crystal structure from the under layer.