Perpendicular Exchange Bias Antiferromagnet Spin Orbit Coupling Memory
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Solution Overview
Problem
Spintronic memory technologies, such as STT-MRAM, face challenges with high voltage and current requirements for writing, leading to reliability issues and slow switching times due to the need for synthetic anti-ferromagnets (SAF) which are difficult to fabricate, especially at high temperatures required for IoT applications.
Innovation Solution
The use of antiferromagnetic (AFM) structures with perpendicular exchange bias instead of SAF, along with a perpendicular magnet via to compensate for dipole fields, reduces the need for SAF and allows for lower programming voltages and faster switching times by enabling perpendicular magnetization switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synthetic anti-ferromagnet (SAF) is used as reference layer, then dipolar interactions are minimized, but fabrication becomes challenging requiring high quality atomic crystallinity, precise thickness, and low roughness
Solution Approach 1:
The patent extracts and eliminates the SAF layer from the magnetic junction structure, replacing it with an antiferromagnetic (AFM) layer. This removal eliminates the complex fabrication requirements of SAF (high quality atomic crystallinity, precise thickness control, low roughness) while maintaining the essential function of minimizing dipolar interactions through the AFM layer's perpendicular exchange bias mechanism
Solution Approach 2:
The patent changes the magnetic anisotropy parameter from in-plane (typical of SAF) to perpendicular orientation. By using an AFM layer with perpendicular magnetization and perpendicular exchange bias, the system achieves dipolar interaction minimization through a different physical mechanism that is more tolerant to fabrication variations in thickness and crystallinity
2Productivity
If large write current is used to write tunnel junction, then switching is achieved, but voltage and current requirements become high leading to reliability issues
Solution Approach 1:
The patent replaces the conventional spin transfer torque (STT) mechanism that requires high current through the tunnel barrier with a spin orbit coupling (SOC) based mechanism. By using a magnetic junction with perpendicular magnetization and AFM layer, the system enables magnetization switching through spin Hall effect or Rashba effect, where spin-polarized current flows through a heavy metal layer adjacent to the magnetic layers, substituting the direct high-current-through-barrier mechanism with a more reliable SOC-based approach
Solution Approach 2:
The patent employs a composite magnetic junction structure consisting of multiple layers including ferromagnetic layers, antiferromagnetic layer, and potentially heavy metal layers for SOC. This composite structure combines materials with different properties (high spin polarization, high spin Hall angle, perpendicular magnetic anisotropy) to achieve low-current switching while maintaining reliability, as the collective behavior of the composite structure enables efficient spin-orbit coupling interactions
3Reliability
If limited write current is used, then reliability is improved, but write error rates increase or switching times become slow
Solution Approach 1:
The patent changes the switching mechanism parameter from spin transfer torque to spin orbit coupling, and changes the magnetization orientation parameter to perpendicular. This combination enables the system to achieve fast switching times (improving productivity) with low write current (maintaining reliability), as the perpendicular magnetization configuration with SOC provides higher switching efficiency and lower damping compared to conventional in-plane magnetization with STT
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 approach results in lower write error rates, faster write times (less than 10 ns), reduced read current through the magnetic junction, and improved reliability of tunneling oxides, while eliminating the fabrication challenges of SAF at high temperatures.
Implementation Method 1
antiferromagnetic (AFM) structures with perpendicular exchange bias instead of SAF
Implementation Method 2
spin orbit coupling (SOC) interconnect
Implementation Method 3
perpendicular magnet via to compensate for dipole fields
Data Source
AI summary
An apparatus is provided which comprises: a magnetic junction including: a first structure comprising a magnet with an unfixed perpendicular magnetic anisotropy (PMA) relative to an x-y plane of a device; a second structure comprising one of a dielectric or metal; a third structure comprising a magnet with fixed PMA, wherein the third structure has an anisotropy axis perpendicular to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures; a fourth structure comprising an antiferromagnetic (AFM) material, the fourth structure adjacent to the third structure; a fifth structure comprising a magnet with PMA, the fifth structure adjacent to the fourth structure; and an interconnect adjacent to the first structure, the interconnect comprising spin orbit material.