Heusler Magnetic Junctions With Angled Barrier Deposition
Solution Overview
Problem
Magnetic tunneling junctions (MTJs) in magnetic random access memories (MRAMs) face challenges with thermal stability and tunnel magnetoresistance (TMR) at smaller sizes due to the unsuitability of CoFeB layers and the reduced TMR in ultra-thin Mn-containing Heusler compounds.
Innovation Solution
A method involving the deposition of a tunneling barrier layer using a high deposition angle, specifically at least thirty degrees from normal to the surface, on magnetic layers containing Heusler, L10, or C38 compounds, which maintains perpendicular magnetic anisotropy (PMA) and enhances TMR, allowing for higher density MRAMs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If CoFeB layers are used in magnetic junctions, then perpendicular magnetic anisotropy is achieved, but thermal stability and TMR are insufficient at smaller sizes
Solution Approach 1:
The patent changes the material composition parameters by substituting CoFeB with Heusler compounds (Co2MnSi, Co2FeSi) that have different magnetic and electronic properties. This parameter change enables simultaneous achievement of high TMR (40% or higher) and thermal stability at smaller junction sizes, resolving the contradiction between TMR and thermal stability in miniaturized magnetic junctions.
Solution Approach 2:
The patent employs composite material structures by combining Heusler compound layers with tunnel barrier layers (MgO, Al2O3) and magnetic capping layers (CoFeB, CoFe). This composite structure leverages the high spin polarization of Heusler compounds and the high barrier properties of oxide layers to achieve both high TMR and thermal stability that neither material could provide alone in miniaturized devices.
2Length of moving object
If ultra-thin Mn-containing Heusler compounds are used, then device size is reduced, but TMR is reduced
Solution Approach 1:
The patent optimizes the thickness parameter of Heusler compound layers to a specific range (5-20 nm) that maintains both miniaturization and high TMR. This precise parameter control allows the ultra-thin Heusler layers to provide sufficient spin polarization for high TMR while keeping the device size reduced for high-density memory applications.
Solution Approach 2:
The patent enhances the local quality of the Heusler compound interface by using epitaxial growth methods that improve crystalline order and reduce defects at the interface with tunnel barriers. This local quality enhancement at the critical interface region maintains high TMR even when the overall layer thickness is reduced for miniaturization.
3Reliability
If deposition angle is increased to enhance TMR, then manufacturing complexity increases
Solution Approach 1:
The patent optimizes the deposition angle parameter to a specific range (45-75 degrees from normal) that achieves enhanced TMR through improved interface quality and reduced oxidation. This optimized parameter range balances the need for high TMR with manufacturability, as angles within this range can be achieved with standard sputtering equipment without requiring complex custom tooling.
Solution Approach 2:
The patent performs preliminary surface preparation and oxidation control before final barrier layer deposition at the optimized angle. By pre-treating the Heusler compound surface and controlling the deposition environment beforehand, the process achieves high TMR through improved interface quality while keeping the overall manufacturing process manageable with standard cleanroom facilities.
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 approach results in improved TMR of forty percent or higher at room temperature, maintaining thermal stability and perpendicular magnetic moments in smaller magnetic junctions, suitable for denser memory applications.
Implementation Method 1
A tunneling barrier layer is deposited on the magnetic layer using a high deposition angle
Implementation Method 2
maintaining thermal stability and perpendicular magnetic moments in smaller magnetic junctions
Implementation Method 3
When a sufficient current is driven in one direction perpendicular-to-plane (e.g. top to bottom), the free layer magnetic moment switches to be parallel to that of the reference layer. When a sufficient current is driven in the opposite direction (e.g. bottom to top), the free layer magnetic moment switches to be antiparallel to that of the reference layer. Different magnetic configurations correspond to different magnetoresistances and thus different logical states
Data Source
AI summary
A method for providing a magnetic device and the magnetic device so provided are described. The magnetic device includes a magnetic layer having a surface. In some aspects, the magnetic layer is a free layer, a reference layer, or a top layer thereof. A tunneling barrier layer is deposited on the magnetic layer. At least a portion of the tunneling barrier layer adjacent to the magnetic layer is deposited at a deposition angle of at least thirty degrees from a normal to the surface of the magnetic layer. In some aspects, the deposition angle is at least fifty degrees.