Single Crystal Diamond Multilayer Substrate for Low-Stress 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 in heteroepitaxial growth on underlying substrates, limiting their application in electronic and magnetic devices.
Innovation Solution
The use of specific initial substrates (e.g., single crystal Si {111} and α-Al2O3 {0001}) combined with intermediate layers (e.g., single crystal Ir film and MgO film) with controlled off-angles to facilitate epitaxial growth of single crystal diamond layers, reducing defects and stress.
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 patent divides the large-area substrate into multiple smaller HPHT-synthesized diamond substrates (each maintaining high crystallinity) and joins them together to form a large-area single crystal diamond substrate, thus achieving both high quality and large size
Solution Approach 2:
The patent combines multiple HPHT diamond substrates into a single large-area substrate through joining processes, merging the advantages of HPHT-synthesized high-quality diamond while achieving the required large area for practical applications
2Area of stationary object
If mosaic method is used to join multiple HPHT substrates, then large area is achieved, but joint imperfections remain
Solution Approach 1:
The patent extracts and removes the problematic joint regions between multiple substrates through selective etching processes, eliminating the source of imperfections while preserving the large-area structure
Solution Approach 2:
The patent uses selective chemical etching that differentiates between diamond crystal orientations, allowing precise removal of misaligned joint regions while preserving the single crystal structure of properly oriented areas
3Area of stationary object
If CVD method is used to grow diamond on underlying substrate, then large area (6 inches diameter) is achieved, but single crystallization is difficult due to lattice mismatch
Solution Approach 1:
The patent introduces an intermediate buffer layer between the CVD-grown diamond and the underlying substrate, which acts as a mediator to accommodate lattice mismatch and enable heteroepitaxial growth of single crystal diamond over large areas
Solution Approach 2:
The patent modifies the growth parameters and substrate conditions during CVD processing to promote single crystal formation, including controlling temperature, pressure, and gas composition to achieve high-quality single crystal diamond on large-area substrates
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 large-diameter, high-crystallinity single crystal diamond layers with few defects and low stress, suitable for electronic and magnetic devices, at a lower cost.
Implementation Method 1
an intermediate layer which comprises a single layer or a laminate film on the initial substrate
Implementation Method 2
an outermost surface on the initial substrate has an off angle in a crystal axis <100> direction relative to a cubic crystal plane orientation {111}, or has an off angle in a crystal axis <0001> or <11-20> direction relative to a hexagonal crystal plane orientation {0001}, or has an off angle in a crystal axis <100> direction relative to a cubic crystal plane orientation {001}, or has an off angle in a crystal axis <0001> or <11-20> direction relative to a hexagonal crystal plane orientation {11-20}
Data Source
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AI summary
The present invention is an underlying substrate for a single crystal diamond laminate substrate, the underlying substrate including an initial substrate being any of a single crystal Si {111} substrate, a single crystal α-Al2O3 {0001} 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 {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. 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.