Magnetic Memory Element with Thick Beta-Phase Heavy Metal Layer
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Solution Overview
Problem
It is challenging to achieve a three-terminal type magnetic memory element with magnetization reversal by spin orbit torque while ensuring a sufficient process margin and reducing the write current, as increasing the heavy metal layer thickness to ensure process margin leads to the formation of the more stable α-phase crystal structure rather than the desired β-phase, which is necessary for large spin orbit torque.
Innovation Solution
A magnetic multilayer film with a heavy metal layer of 5d transition metals like Ta or W, having an amorphous or β-phase crystal structure and a thickness of 6 nm or more, is used, along with a ferromagnetic layer with reversible magnetization, to facilitate magnetization reversal by spin orbit torque while ensuring a process margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heavy metal layer thickness is increased to ensure process margin, then the process margin is improved, but the crystal structure changes from β-phase to more stable α-phase, reducing spin orbit torque efficiency
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the heavy metal layer to be 6 nm or more while maintaining the β-phase crystal structure. This is achieved by adjusting deposition conditions and using specific materials (Ta or W) to sustain the metastable β-phase at the required thickness, thereby resolving the contradiction between ensuring process margin and maintaining spin orbit torque efficiency.
2Reliability
If the heavy metal layer thickness is increased to ensure process margin, then the process margin is improved, but the write current increases
Solution Approach 1:
The patent resolves this contradiction by optimizing the thickness parameter of the heavy metal layer to be 6 nm or more, which ensures sufficient process margin while preventing excessive write current increase. The controlled thickness maintains efficient spin orbit torque generation, thereby keeping write current at acceptable levels despite the increased thickness for process reliability.
3Reliability
If a thick heavy metal layer is used to ensure process margin, then the process margin is improved, but the magnetization reversal efficiency decreases
Solution Approach 1:
The patent addresses this contradiction by precisely controlling the heavy metal layer thickness to be 6 nm or more while maintaining the metastable β-phase crystal structure. This parameter optimization ensures that the layer is thick enough for process margin but thin enough to maintain efficient magnetization reversal through spin orbit torque, preventing the efficiency degradation that would occur with excessive thickness.
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 allows for a magnetic memory element with reduced write current and maintained process margin, enabling efficient magnetization reversal and stable operation.
Implementation Method 1
magnetization reversal by a spin orbit torque... spin-polarized electrons are accumulated on a layer made from a ferromagnetic material, which exerts a torque on a magnetization direction
Implementation Method 2
a tunnel magneto resistance (TMR) effect is utilized in which a tunnel resistance of the magnetic tunnel junction varies with a relative angle between a magnetization direction of the recording layer and that of the reference layer
Implementation Method 3
magnetization reversal by a spin-transfer torque (STT) was demonstrated that reverses a magnetization direction with an angular momentum transferred between a spin-polarized electron and a magnetization
Data Source
AI summary
The magnetic memory element (100) includes: a conductive layer that includes a heavy metal layer (10) containing a 5d transition metal; a first ferromagnetic layer (20) that is adjacent to the conductive layer and contains a ferromagnetic layer having a reversible magnetization; a barrier layer (30) that is adjacent to the first ferromagnetic layer (20) and includes an insulating material; a reference layer (40) that is adjacent to the barrier layer (30) and has at least one second ferromagnetic layer (41) having a fixed magnetization direction; a cap layer (50) that is adjacent to the reference layer (40) and includes a conductive material; a first terminal (T1) that is capable of introducing a current into one end of the heavy metal layer (10) in the longitudinal direction; a second terminal (T2) that is capable of introducing a current into the other end of the heavy metal layer (10) in the longitudinal direction; and a third terminal (T3) that is capable of introducing a current into the cap layer (50).