TMR Structures with Segmented MgO Barrier
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Solution Overview
Problem
Existing tunnel magnetoresistance (TMR) structures face limitations in achieving high tunneling magnetoresistance (TMR) values and low resistance area (RA) products due to the formation methods of magnesium oxide tunnel barrier layers, particularly with reactive deposition techniques which struggle to uniformly oxidize thick magnesium layers.
Innovation Solution
The method involves forming magnesium layers above a free or reference layer and exposing them to an oxidizing environment for natural oxidation, creating a tunnel barrier layer with a microstructure and composition characteristic of in situ natural oxidation of magnesium, which can be combined with reactive deposition to achieve improved TMR/RA ratios and breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reactive deposition is used to form magnesium oxide tunnel barrier layers, then the barrier layer can be formed with controlled thickness, but the TMR/RA ratio and breakdown voltage are limited due to inability to uniformly oxidize thick magnesium layers
Solution Approach 1:
The tunnel barrier layer formation is segmented into multiple sequential steps: depositing a first magnesium layer, oxidizing it to form a first magnesium oxide layer, then depositing a second magnesium layer and oxidizing it to form a second magnesium oxide layer. This segmentation allows each layer to be optimized independently, achieving both thickness control and high TMR/RA ratio with breakdown voltage exceeding 5V.
Solution Approach 2:
The magnesium layers are deposited and oxidized in advance before final device assembly, creating a pre-formed tunnel barrier structure with optimized properties. This preliminary formation of the barrier layer ensures uniform oxidation and controlled thickness before the device is completed.
2Length of stationary object
If thick magnesium layers are used to form tunnel barrier layers, then the barrier thickness can be increased for better insulation, but uniform oxidation becomes difficult achieving high TMR values
Solution Approach 1:
The thick magnesium barrier is segmented into multiple thinner magnesium layers (first magnesium layer and second magnesium layer), each being oxidized separately. This ensures uniform oxidation across the entire barrier thickness while achieving the desired total thickness for proper insulation properties.
Solution Approach 2:
Each magnesium layer is oxidized to a controlled extent to form magnesium oxide layers that collectively provide the required total thickness. The oxidation is applied partially to each layer rather than attempting to oxidize one thick layer excessively, ensuring uniformity.
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 higher TMR/RA ratios, lower interlayer coupling, and increased breakdown voltage compared to tunnel barrier layers formed exclusively by reactive deposition, enhancing the performance and reliability of TMR systems.
Implementation Method 1
exposing the first layer of magnesium to an oxidizing environment for causing oxidation of the first layer of magnesium
Implementation Method 2
tunnel magnetoresistance (TMR) structures
Data Source
AI summary
A method in one embodiment includes forming a first layer of magnesium above at least one of a free layer and a reference layer; exposing the first layer of magnesium to an oxidizing environment for causing oxidation of the first layer of magnesium; forming a second layer of magnesium above the oxidized first layer of magnesium; and exposing the second layer of magnesium to the oxidizing environment for causing oxidation of the second layer of magnesium. A system in one embodiment includes a free layer; and a tunnel barrier layer having microstructure and composition characteristic of in situ natural oxidation of magnesium. Additional systems and methods are also presented.