Diamond Laminate Substrate with Intermediate Layer for Low-Defect Epitaxy
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Solution Overview
Problem
Current methods for producing single crystal diamond substrates face challenges in achieving large area, high quality, and low stress substrates due to lattice mismatch and imperfections, limiting their applicability in electronic and magnetic devices.
Innovation Solution
An underlying substrate comprising specific single crystal materials with controlled off-angles and intermediate layers, such as single crystal Si, α-Al2O3, and metal oxide films, is used to facilitate epitaxial growth of high-quality single crystal diamond layers with controlled off-angles, mitigating lattice mismatch and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If HPHT method is used to synthesize single crystal diamond, then high purity and single crystallinity are achieved, but the substrate size is limited to approximately 8 mm square and contains nitrogen impurities
Solution Approach 1:
The invention uses multiple small HPHT diamond substrates (each with high crystallinity) and joins them together through a mosaic method to create a larger composite substrate. This segmentation approach allows maintaining the high quality characteristics of individual small substrates while achieving a larger overall area suitable for practical applications.
2Area of stationary object
If mosaic method is used to join multiple HPHT substrates, then large area substrate is achieved, but imperfections in the joints remain
Solution Approach 1:
The invention introduces an intermediate layer between the HPHT diamond substrates during the mosaic joining process. This intermediate layer acts as a mediator that facilitates better bonding between substrates, reduces joint imperfections, and improves the overall quality and reliability of the connections while enabling large area substrate creation.
3Area of stationary object
If CVD method is used to grow diamond on polycrystal substrate, then large area (6 inches diameter) and high purity are achieved, but single crystallinity is difficult to obtain due to lattice mismatch
Solution Approach 1:
The invention employs an intermediate layer with lattice constant and thermal expansion coefficient values between those of the polycrystal substrate and diamond. This intermediate layer serves as a lattice-matched mediator that enables epitaxial growth of single crystal diamond on polycrystal substrates, achieving both large area and high crystallinity that would otherwise be incompatible.
Solution Approach 2:
The invention changes the physical and chemical parameters of the substrate system by introducing an intermediate layer with specific lattice constant and thermal expansion properties. This parameter adjustment creates a gradient transition that accommodates the large lattice mismatch between polycrystal substrates and diamond, enabling successful epitaxial growth of single crystal diamond over large areas.
4Area of stationary object
If heteroepitaxial growth is attempted on conventional substrates like Si, then large area growth is possible, but the 34.3% lattice constant difference causes severe defects
Solution Approach 1:
The invention introduces an intermediate layer with lattice constant and thermal expansion coefficient values intermediate between the substrate and diamond. This intermediate layer acts as a lattice-matched mediator that enables epitaxial growth of single crystal diamond on polycrystal substrates, achieving both large area and high crystallinity that would otherwise be incompatible.
Solution Approach 2:
The invention changes the physical and chemical parameters of the substrate system by introducing an intermediate layer with specific lattice constant and thermal expansion properties. This parameter adjustment creates a gradient transition that accommodates the large lattice mismatch between polycrystal substrates and diamond, enabling successful epitaxial growth of single crystal diamond over large areas.
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 enables the production of large-diameter, high-crystallinity single crystal diamond layers with few defects and low stress, suitable for electronic and magnetic devices, and allows for the creation of freestanding diamond structures.
Implementation Method 1
a combination of suitable materials, as an underlying substrate for forming the diamond with small differences in lattice constants and linear expansion coefficients with the diamond
Implementation Method 2
performing a bias treatment on a surface of the intermediate layer of the underlying substrate to form a diamond nucleus; and growing the diamond nucleus formed on the intermediate layer to perform epitaxial growth, thereby forming a single crystal diamond layer
Data Source
AI summary
An underlying substrate for a single crystal diamond laminate substrate, the underlying substrate including an initial substrate being any of a single crystal Si substrate, a single crystal α-Al2O3 substrate, etc., and an intermediate layer on the initial substrate, in which an outermost surface on the initial substrate has an off angle in a crystal axis <−1-12> direction relative to a cubic crystal plane orientation, or has an off angle in a crystal axis <10-10> or <11-20> direction relative to a hexagonal crystal plane orientation, etc. This provides the underlying substrate capable of forming a single crystal diamond layer having a large area (large diameter), high crystallinity, few hillocks, few abnormal growth particles such as twin crystals, few dislocation defects, etc., high purity, low stress, and high quality and applicable to an electronic and magnetic device.