Laminated Intermediate Layer for Thin Film Warpage Control
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Solution Overview
Problem
Existing methods for producing polycrystalline thin films with high crystal orientation face challenges such as warpage due to internal stress and low productivity, particularly when using thick intermediate layers like Gd2Zr2O7, which limits the thickness of oxide superconductors and increases manufacturing time and cost.
Innovation Solution
A method involving a laminated intermediate layer with a rock-salt crystal structure (e.g., MgO) and a fluorite crystal structure (e.g., GZO) is used, allowing for a thinner intermediate layer while maintaining high crystal orientation, reducing internal stress, and preventing warpage, thereby enhancing manufacturing speed and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a thick intermediate layer (e.g., Gd2Zr2O7) is used to maintain high crystal orientation, then crystal orientation is improved, but internal stress increases causing warpage and productivity decreases
Solution Approach 1:
The intermediate layer is divided into two distinct layers: a first intermediate layer (MgO with rock-salt structure) and a second intermediate layer (Gd2Zr2O7 with fluorite structure). This segmentation allows each layer to perform its specific function - the MgO layer provides strong template effect for crystal orientation, while the Gd2Zr2O7 layer provides buffer characteristics. The combined thickness is reduced to 1-5 μm while maintaining high crystal orientation and reducing internal stress compared to using a single thick layer.
Solution Approach 2:
The patent uses a composite intermediate layer structure combining MgO (rock-salt crystal structure) and Gd2Zr2O7 (fluorite crystal structure). These two materials have complementary properties: MgO provides excellent lattice matching and template effect for high crystal orientation, while Gd2Zr2O7 provides intermediate physical characteristics between the substrate and superconductor. The composite structure achieves both high crystal orientation and reduced internal stress with thinner total thickness.
2Reliability
If a thick intermediate layer is used to prevent peeling-off, then adhesion is improved, but film thickness increases causing warpage
Solution Approach 1:
The intermediate layer is segmented into two functional layers with different thicknesses and properties. The first MgO layer (thinner) provides strong adhesion through excellent lattice matching and template effect, while the second Gd2Zr2O7 layer (thicker) provides mechanical buffer characteristics. This segmentation achieves reliable adhesion with reduced total thickness, preventing warpage that would occur with a single thick layer.
Solution Approach 2:
The patent changes the physical and chemical parameters of the intermediate layer by using two different materials with distinct properties. The MgO layer has rock-salt crystal structure with specific lattice constants that provide excellent matching, while Gd2Zr2O7 has fluorite structure with intermediate physical characteristics. By optimizing the thickness ratio and material composition, the patent achieves strong adhesion while controlling internal stress to prevent warpage.
3Manufacturing precision
If ion beam assist method (IBAD) is used to achieve high in-plane orientation, then crystal orientation is improved, but deposition rate decreases
Solution Approach 1:
The deposition process is segmented into two stages corresponding to the two layers. The first MgO layer is deposited using IBAD method to establish strong in-plane orientation and template structure. The second Gd2Zr2O7 layer is then deposited to provide buffer characteristics. This segmentation allows the orientation-critical first layer to use IBAD while the second layer can be optimized for other properties, achieving both high orientation and improved overall productivity.
Solution Approach 2:
The first MgO intermediate layer is formed in advance using IBAD method to create a strong template structure with high in-plane orientation. This preliminary action establishes the crystal orientation framework that guides the subsequent deposition of the oxide superconductor layer. By performing this orientation-critical step first with a thinner layer, the patent achieves high orientation while reducing the time-consuming IBAD process duration.
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 configuration enables the production of polycrystalline thin films with reduced internal stress, preventing warpage and allowing for higher critical current density and superconductivity, while significantly increasing manufacturing speed and reducing costs by using thinner intermediate layers.
Implementation Method 1
The intermediate layer consists mainly of MgO, YSZ (yttria-stabilized zirconium), SrTiO3 or the like each having a physical characteristic value, such as a coefficient of thermal expansion and a lattice constant, intermediate with respect to the values of the substrate and the superconductor.
Implementation Method 2
A difference in coefficients of thermal expansion and lattice constants between the substrate and the superconductor may cause distortion in the superconductor or peeling-off of the oxide superconductor film from the substrate during a cooling process to a superconducting critical temperature.
Implementation Method 3
In the IBAD method, constituent particles ejected from a target by sputtering are deposited on a substrate while being irradiated with argon ions, oxygen ions or other ions at the same time emitted from an ion gun at a tilted angle (e.g., 45 degrees).
Implementation Method 4
In the IBAD method, constituent particles ejected from a target by sputtering are deposited on a substrate while being irradiated with argon ions, oxygen ions or other ions at the same time emitted from an ion gun at a tilted angle (e.g., 45 degrees).
Data Source
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AI summary
An object of the invention is to provide a polycrystalline thin film which includes an intermediate layer that is made thinner while keeping high crystal orientation so as to prevent warpage of a substrate resulting from internal stress of the film. A polycrystalline thin film according to the invention includes an intermediate layer formed by a first layer and a second layer laminated in this order and provided on a metal substrate. The first layer has a rock-salt crystal structure and the second layer has a fluorite crystal structure.