Amorphous XN Layer in Magnetic Tunnel Junctions
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Solution Overview
Problem
Boron in the CoFe/MgO interface or inside the MgO lattice in magnetic tunnel junctions undesirably reduces tunneling magnetoresistance (TMR), and existing technologies do not encompass an amorphous and non-stoichiometric N-rich layer.
Innovation Solution
Incorporating a non-stoichiometrically N-rich amorphous XN layer, where X is one or more of W, Mo, Cr, V, Nb, Ta, Al, and Ti, between the CoFe and MgO layers to reduce conductivity and facilitate crystallization of CoFe into a bcc 001 lattice, thereby minimizing the impact of Boron on TMR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If CoFe is deposited as amorphous and crystallized by annealing at high temperature (≥250°C) to achieve bcc 001 lattice, then crystalline structure is achieved, but Boron diffuses out and accumulates at CoFe/MgO interface reducing TMR
Solution Approach 1:
An amorphous XN layer (where X is W, Mo, Cr, V, Nb, Ta, Al, or Ti) is introduced as an intermediary between CoFe and MgO. This layer prevents Boron diffusion to the CoFe/MgO interface while maintaining the bcc 001 crystalline structure of CoFe, thereby preserving high TMR values.
Solution Approach 2:
The amorphous XN layer serves as a sacrificial or temporary structure that absorbs the harmful effect of Boron diffusion. By being positioned between CoFe and MgO, it captures Boron atoms that would otherwise migrate to the critical interface, protecting the TMR property without requiring complex process modifications.
2Manufacturing precision
If annealing temperature is increased to ensure complete crystallization of CoFe, then bcc 001 lattice formation is improved, but Boron diffusion and TMR reduction are exacerbated
Solution Approach 1:
The amorphous XN layer acts as a diffusion barrier that decouples the crystallization process from Boron migration. This allows annealing to proceed at temperatures sufficient for complete CoFe crystallization into bcc 001 structure without the penalty of increased Boron diffusion to the MgO interface, as the XN layer intercepts and retains Boron atoms.
3Reliability
If MgO tunnel insulator is made thinner to improve tunneling current, then conductivity increases, but sensitivity to interface contamination (Boron) increases
Solution Approach 1:
The amorphous XN layer serves as a protective intermediary that shields the MgO tunnel insulator from Boron contamination. This allows the use of thinner MgO layers to achieve higher tunneling currents while the XN layer prevents Boron from reaching the critical MgO/CoFe interface, thereby maintaining low sensitivity to interface contamination.
4Use of energy by moving object
If write current is reduced to lower power consumption, then energy efficiency improves, but spin pumping reduction becomes insufficient to maintain switching performance
Solution Approach 1:
The patent converts the potential harm of reduced write current (insufficient spin pumping) into a benefit by utilizing the amorphous XN layer's ability to reduce spin pumping losses. The XN layer modifies the spin transport properties, reducing unwanted spin pumping effects that would otherwise require higher write currents, thereby enabling low-power operation while maintaining switching performance.
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 reduces the required write current in magnetic tunnel junctions by lowering spin pumping and maintaining or improving magnetic tunneling properties, achieving a balance of low switching current and high retention.
Implementation Method 1
This approach reduces the required write current in magnetic tunnel junctions by lowering spin pumping
Implementation Method 2
using a spin-polarized current to result in a spin-transfer torque (STT) effect. By passing a current through certain magnetic material (sometimes also referred to as polarizer material), one can produce a spin-polarized current. If a spin-polarized current is directed into a magnetic material, spin angular momentum can be transferred to that material, thereby affecting its magnetization orientation.
Implementation Method 3
A magnetic tunnel junction is an integrated circuit component having two conductive magnetic electrodes separated by a thin non-magnetic tunnel insulator material (e.g., dielectric material). The insulator material is sufficiently thin such that electrons can tunnel from one magnetic electrode to the other through the insulator material under appropriate conditions.
Implementation Method 4
Ideally such materials are each crystalline having a body-centered-cubic (bcc) 001 lattice. During and/or after the depositing, the MgO tunnel insulator, the CoFe, and the tunnel insulator ideally individually achieve a uniform bcc 001 lattice structure.
Data Source
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AI summary
A magnetic tunnel junction comprises a conductive first magnetic electrode comprising magnetic recording material. A conductive second magnetic electrode is spaced from the first electrode and comprises magnetic reference material. A non-magnetic tunnel insulator material is between the first and second electrodes. The magnetic recording material of the first electrode comprises a first crystalline magnetic region, in one embodiment comprising Co and Fe. In one embodiment, the first electrode comprises a second amorphous region comprising amorphous XN, where X is one or more of W, Mo, Cr, V, Nb, Ta, Al, and Ti. In one embodiment, the first electrode comprises a second region comprising Co, Fe, and N.