MgO Tunnel Barrier Oxidation at Cryogenic Temperature
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Solution Overview
Problem
Existing methods for manufacturing magnetoresistive elements face challenges in suppressing the oxidation of the underlying ferromagnetic layer during the formation of a magnesium oxide layer, which affects the quality and performance of the magnetoresistive element.
Innovation Solution
A method involving the oxidation of a magnesium layer to form a magnesium oxide layer at a substrate temperature of 150 Kelvin or less, combined with controlled oxidation rates in the depth direction, is employed to minimize oxidation of the underlying ferromagnetic layer, followed by increasing the temperature to enhance crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxygen gas is supplied to oxidize the magnesium layer at conventional temperatures, then the magnesium oxide layer is formed, but the underlying ferromagnetic layer is also oxidized
Solution Approach 1:
The patent applies parameter changes by controlling the substrate temperature to 150 Kelvin or less during oxidation. This temperature parameter control selectively suppresses the oxidation reaction of the ferromagnetic layer while allowing the magnesium layer to form magnesium oxide, thereby resolving the contradiction between forming the tunnel barrier and preventing unwanted oxidation
Solution Approach 2:
The patent applies local quality by creating different oxidation conditions for different layers. The magnesium layer is oxidized to form the tunnel barrier, while the ferromagnetic layer is protected from oxidation through low temperature control, achieving selective oxidation with different properties for different regions/layers
2Object-affected harmful factors
If the substrate temperature is kept low during oxidation, then ferromagnetic layer oxidation is suppressed, but the crystallinity of the magnesium oxide layer is reduced
Solution Approach 1:
The patent applies segmentation by dividing the oxidation process into two distinct stages: first oxidizing the magnesium layer at low temperature (≤150K) to prevent ferromagnetic layer oxidation, then increasing the temperature to enhance the crystallinity of the formed magnesium oxide layer. This temporal and thermal segmentation resolves the contradiction between preventing oxidation and achieving crystallinity
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 the production of magnetoresistive elements with a low resistance area product and high MR ratio, while effectively preventing oxidation of the ferromagnetic layer and enhancing the crystallinity of the magnesium oxide layer.
Implementation Method 1
oxidizing the magnesium layer by supplying oxygen gas to the substrate in a state where a temperature of the substrate support is set to 150 Kelvin or less
Implementation Method 2
oxidizing the magnesium layer by supplying oxygen gas to the substrate... so as to form a magnesium oxide layer from the magnesium layer
Implementation Method 3
followed by increasing the temperature to enhance crystallinity
Data Source
AI summary
There is provided a method of manufacturing a magnetoresistive element. The method comprises: (a) placing a substrate on a substrate support of an oxidation processing apparatus, the substrate having a ferromagnetic layer and a magnesium layer provided on the ferromagnetic layer; and (b) oxidizing the magnesium layer by supplying oxygen gas to the substrate in a state where a temperature of the substrate support is set to 150 Kelvin or less to form a magnesium oxide layer from the magnesium layer.