Vertical Transistor Structure for High Density Spin Orbit Torque MRAM
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional MRAM devices face challenges in reliability and endurance due to shared read and write paths, leading to dielectric breakdown and read disturbance, while spin orbit torque MRAM devices require large transistors to handle high switching currents, increasing cost and reducing density.
Innovation Solution
A spin orbit torque data recording device with a vertical transistor structure that selectively supplies electrical current to the spin orbit torque layer, using a semiconductor pillar and gate dielectric layer to manage high current loads efficiently, reducing transistor size and improving durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional two-terminal MRAM devices are used, then read and write operations can be performed, but the shared read and write paths cause dielectric breakdown and read disturbance, reducing reliability and endurance
Solution Approach 1:
The patent divides the current path into separate read and write paths by introducing a spin orbit torque layer. Write current flows through the spin orbit torque layer to generate spin torque, while read current flows through the magnetic tunnel junction separately. This segmentation eliminates the shared path problem and prevents dielectric breakdown and read disturbance.
Solution Approach 2:
The spin orbit torque layer acts as an intermediary that converts charge current into spin torque to switch the magnetic state. This intermediary mechanism allows write operations without requiring high current through the magnetic tunnel junction barrier, thereby eliminating dielectric breakdown while maintaining separate read and write paths.
2Reliability
If spin orbit torque MRAM devices are used with generic spin orbit torque layers, then read and write current paths are separated improving reliability, but the high switching current density requires large transistors, increasing cost and reducing density
Solution Approach 1:
The patent changes the material parameter of the spin orbit torque layer by using topological insulator materials with high spin-orbit coupling strength. This material parameter change reduces the required switching current density from 1-2×10^8 A/cm² to lower values, enabling smaller transistor sizes and higher device density while maintaining separate read and write paths.
Solution Approach 2:
The patent employs composite material structures combining topological insulator spin orbit torque layers with magnetic tunnel junctions. This composite approach leverages the unique properties of topological insulators (strong spin-orbit coupling, high conductivity) to achieve low switching current density, thereby reducing transistor size requirements while maintaining reliability through current path separation.
3Ease of operation
If the barrier layer in the MTJ is made thin to allow sufficient write current flow, then switching can be achieved, but the thin barrier layer becomes more susceptible to dielectric breakdown from repeated write operations
Solution Approach 1:
The spin orbit torque layer serves as an intermediary that generates spin torque from charge current to switch the magnetic state. This mechanism enables write operations without requiring high current through the barrier layer, allowing the use of thin barrier layers for good switching capability while avoiding dielectric breakdown through the intermediary spin torque mechanism.
Solution Approach 2:
The patent replaces the direct electrical switching mechanism (current through barrier) with a spin torque mechanism. Instead of relying on high current flow through the barrier layer to switch states, the spin orbit torque layer converts charge current into spin angular momentum that acts on the magnetic moment, enabling switching without high barrier current and thus preventing dielectric breakdown.
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
The vertical transistor structure effectively handles high current loads while minimizing wafer real estate, enhancing the durability and density of spin orbit torque MRAM devices by separating read and write currents and reducing stress on the barrier layer.
Implementation Method 1
Spin orbit torque based MRAM devices show switching speeds down to about 200 ps
Implementation Method 2
Magnetoresistive Random Access Memory (MRAM) is a non-volatile memory technology
Data Source
AI summary
A spin orbit torque memory device having a vertical transistor structure. The spin orbit torque memory device includes a magnetic memory element such as a magnetic tunnel junction formed on a spin orbit torque layer. The vertical transistor structure selectively provides an electrical current to the spin orbit torque layer to switch a memory state of the magnetic memory element. The vertical transistor structure accommodates the relatively high electrical current needed to provide spin orbit torque switching while also consuming a small amount of wafer real estate. The vertical transistor structure can include a semiconductor pillar structure surrounded by a gate dielectric layer and a gate structure such that the gate dielectric layer separates the gate structure from the semiconductor pillar.