Tapered MTJ Element with Amorphous Tunnel Barrier
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Solution Overview
Problem
The existing magnetic tunnel junction (MTJ) elements in magnetoresistive random access memory (MRAM) face challenges in reducing write/erase current and improving magnetoresistive ratio (MR ratio) while maintaining high data retention, due to variations in the planarity of underlayers and element isolation processes.
Innovation Solution
The MTJ element is designed with a tunnel barrier layer having an amorphous state on its side surface, achieved through neon ion beam etching, which reduces leakage magnetic field influence and prevents short circuits, and the use of specific materials and structures such as CoFeB and MgO to enhance magnetic and electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional MTJ element structure and manufacturing method are used, then the device can be manufactured with standard processes, but the write/erase current is high and MR ratio is insufficient
Solution Approach 1:
The patent applies local quality by creating a tapered structure where the magnetic layer thickness varies spatially - thinner at the center and thicker at the edges. This local variation in thickness optimizes the magnetic properties at different locations, enabling reduced write/erase current while maintaining data retention characteristics.
Solution Approach 2:
The patent changes the physical parameter of magnetic layer thickness from uniform to tapered gradient. This parameter change creates optimal magnetic anisotropy and tunneling conditions that reduce the current required for magnetization switching while preserving data retention.
2Manufacturing precision
If the planarity of underlayer varies, then manufacturing flexibility is maintained, but the MTJ element characteristics lower or vary
Solution Approach 1:
The patent performs preliminary action by forming a planarization layer or adjusting the substrate before depositing the magnetic layers. This preliminary planarization ensures that subsequent layers are deposited on a flat surface, maintaining consistent MTJ element characteristics even when underlying layers have varying planarity.
Solution Approach 2:
The tapered magnetic layer structure creates local quality variations that compensate for underlayer planarity issues. The gradient thickness profile ensures optimal tunneling conditions are achieved locally across the device area, reducing sensitivity to global planarity variations.
3Reliability
If element isolation process is applied, then device integration is enabled, but MTJ element characteristics are degraded
Solution Approach 1:
The patent introduces an intermediary protective layer or capping layer that shields the MTJ element during the isolation process. This intermediary structure prevents damage to the magnetic layers while enabling necessary isolation steps for device integration.
Solution Approach 2:
The tapered magnetic layer structure changes the physical parameters of the MTJ element, making it more robust against isolation process effects. The gradient thickness provides mechanical and magnetic stability that maintains characteristics during subsequent processing steps.
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 magnetization switching characteristics, reduced switching current, and excellent retention characteristics, with a magnetoresistive ratio of 100% or more and suppressed degradation of electrical characteristics.
Implementation Method 1
A magnetic memory device using a tunneling magnetoresistive (TMR) effect is used as a memory cell for storing information
Implementation Method 2
achieved through neon ion beam etching
Implementation Method 3
The tunnel barrier layer has a region in an amorphous state on a side surface
Data Source
AI summary
According to one embodiment, a magnetic memory device includes: a first magnetic layer; a nonmagnetic layer on the first magnetic layer; a second magnetic layer on the nonmagnetic layer; and an insulator film on the nonmagnetic layer surrounding a side surface of the second magnetic layer. The second magnetic layer has an area of a surface facing the nonmagnetic layer smaller than that of the nonmagnetic layer. The nonmagnetic layer includes a first region that is provided between the first magnetic layer and the insulator film. The first region includes an amorphous state.