Copper-Laminated Epitaxial Substrate for Stable (200) Orientation
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Solution Overview
Problem
In substrates for epitaxial growth, irregular parts with non-(200) plane orientations appear after heat treatment, reducing the c-axis orientation ratio and affecting the crystal orientation of superconducting wires, which is attributed to mechanical polishing introducing cutting strains that interfere with the desired (200) plane orientation.
Innovation Solution
A method involving surface-activated bonding of a copper layer with an fcc rolling texture to a metal base material, followed by controlled mechanical polishing and orientation heat treatment, where the (200) plane ratios before and after lamination are maintained within specific limits to inhibit the formation of irregular parts, ensuring a high degree of biaxial crystal orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the copper layer is highly oriented to (200) plane before lamination, then crystal orientation is improved, but the orientation may not be maintained after heat treatment due to cutting strains from polishing
Solution Approach 1:
The invention performs preliminary crystal orientation of the copper layer to the (200) plane before lamination, ensuring that the copper layer has high orientation degree initially. This preliminary action is followed by controlled polishing with specific Ra and Rz parameters that do not disrupt the pre-established orientation, thereby maintaining stability after subsequent heat treatment.
2Strength
If surface adsorbates are removed by sputter etching before bonding, then bonding quality is improved, but the copper layer may become more susceptible to orientation irregularities
Solution Approach 1:
The invention maintains high crystal orientation uniformity through controlled polishing parameters (Ra: 0.01-0.5 μm, Rz: 0.05-2.0 μm) that are applied after sputter etching. These parameter controls ensure that the copper layer surface is properly prepared for bonding while preventing the formation of irregular parts that could compromise orientation 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
The method effectively inhibits the appearance of irregular parts, achieving a high degree of biaxial crystal orientation in the copper layer, leading to improved properties of superconducting wires with enhanced crystal orientation and reduced surface roughness.
Implementation Method 1
a step of crystal-orienting the copper by heating the bonded laminate at a temperature higher than the crystal orientation temperature of copper
Implementation Method 2
a step of sputter etching the surface of a copper foil rolling-processed at a rolling reduction ratio of 90% or more while maintaining the foil at a temperature lower than the crystal orientation temperature to remove a surface adsorbate thereon
Data Source
AI summary
It is an object to provide a substrate for epitaxial growth having a metal base material laminated with a copper layer. On a surface of the copper layer, an area occupied by crystal grains having crystal orientations other than a (200) plane present within 3 μm from the surface can be less than 1.5%. A surface roughness along a same direction as a rolling direction per unit length of 60 μm when measured by AFM can be Ra1<10 nm.