Underlying Substrate for Single Crystal Diamond Laminate
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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 suitable for electronic and magnetic devices, due to issues with nitrogen impurities, limited size, and imperfections in mosaic methods, as well as difficulties in heteroepitaxial growth on suitable substrates.
Innovation Solution
The development of an underlying substrate for a single crystal diamond laminate substrate, comprising an initial substrate such as single crystal Si or α-Al2O3, combined with an intermediate layer of materials like Ir, MgO, or yttria-stabilized zirconia, which allows for the growth of a single crystal diamond layer with specific off angles to enhance crystallinity and reduce defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If HPHT method is used to synthesize single crystal diamond, then high purity diamond can be obtained, but the substrate size is limited to approximately 8 mm square
Solution Approach 1:
The invention uses multiple small HPHT diamond substrates (each approximately 8 mm square with high purity) and joins them together through a mosaic method to create a larger composite substrate. This segmentation approach allows the high purity benefit of small HPHT substrates to be combined with the large area benefit of multiple joined substrates.
Solution Approach 2:
The invention combines multiple HPHT diamond substrates into a single large-area mosaic substrate by joining them together. This merging of multiple small high-purity substrates creates a large substrate that maintains the purity characteristics while achieving the required area for practical applications.
2Area of stationary object
If mosaic method is used to join HPHT substrates, then large area substrate can be obtained, but imperfections in the joints remain
Solution Approach 1:
The invention introduces a carefully designed intermediate layer between the HPHT diamond substrates during joining. This intermediate layer acts as a mediator that facilitates better bonding and reduces joint imperfections, improving the overall quality of the mosaic substrate while maintaining large area.
Solution Approach 2:
The invention optimizes various parameters of the joining process including temperature, pressure, and the composition/thickness of the intermediate layer. By changing these parameters, the joint quality is improved while maintaining the large substrate area achieved through the mosaic method.
3Area of stationary object
If CVD method is used to grow diamond on polycrystal substrates, then large area diamond can be obtained, but single crystallization is difficult due to lattice mismatch
Solution Approach 1:
The invention uses an intermediate layer with specific crystal structure and lattice constant that serves as a mediator between the polycrystal substrate and the diamond layer. This intermediate layer reduces the lattice mismatch effect, enabling successful heteroepitaxial growth of single crystal diamond on large-area polycrystal substrates.
Solution Approach 2:
The invention creates a composite structure consisting of the polycrystal substrate, the intermediate layer, and the single crystal diamond layer. This composite material approach allows combining the large area benefit of polycrystal substrates with the high crystallinity of single crystal diamond through the mediating intermediate layer.
4Ease of manufacture
If heteroepitaxial growth is attempted on substrates with large lattice mismatch (e.g., Si), then growth can proceed, but crystallinity and quality deteriorate due to 34.3% lattice constant difference
Solution Approach 1:
The invention introduces an intermediate layer with gradient lattice constant or specific crystal structure that acts as a mediator between the Si substrate and diamond. This intermediate layer progressively reduces the lattice mismatch, enabling heteroepitaxial growth to proceed while maintaining high crystal quality despite the large 34.3% lattice constant difference.
Solution Approach 2:
The invention changes the lattice constant parameter progressively through the intermediate layer, creating a gradient that reduces the abrupt mismatch. This parameter change approach allows heteroepitaxial growth to proceed on Si substrates while maintaining acceptable crystal quality by reducing the effective lattice mismatch at each interface.
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 enables the production of single crystal diamond substrates with large diameters, high crystallinity, few defects, and high purity, suitable for electronic and magnetic devices, while also allowing for the production of single crystal diamond freestanding structure substrates.
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
it is very difficult to grow the diamond heteroepitaxially on a surface of the underlying substrate
Implementation Method 3
a vapor deposition (Chemical Vapor Deposition: CVD) method can provide large-area diamonds
Data Source
AI summary
An underlying substrate for a single crystal diamond laminate substrate includes an initial substrate being any of a single crystal Si {111} substrate and a single crystal α-Al2O3 {0001} substrate, etc., an intermediate layer on the initial substrate, in which an outermost surface on the initial substrate has no off angle, or has an off angle in a crystal axis <−1-12> direction relative to a cubic crystal plane orientation {111}, or has an off angle in a crystal axis <10-10> or <11-20> direction relative to a hexagonal crystal plane orientation {0001}, etc. Thereby, the underlying substrate is provided, in which the substrate is capable of forming a single crystal diamond layer having a large area (large diameter), high crystallinity, few hillocks, few abnormal growth particles, few dislocation defects, etc., high purity, low stress, and high quality, and applicable to an electronic and magnetic device.