Diamond Multilayer Substrate with Intermediate Layer 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 suitable for electronic and magnetic devices due to imperfections in jointed HPHT substrates and difficulties in growing diamond heteroepitaxially on suitable underlying substrates with minimal lattice mismatch.
Innovation Solution
An underlying substrate with specific initial substrates such as single crystal Si or α-Al2O3, combined with intermediate layers like Ir or MgO films, is used to form a single crystal diamond layer with controlled off-angles, enabling large diameter, high crystallinity, and low stress diamond growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If HPHT method is used to synthesize single crystal diamond, then single crystal quality is achieved, but substrate size is limited to approximately 8 mm square and contains nitrogen impurities
Solution Approach 1:
The invention segments the substrate system into three distinct parts: an initial substrate (Si, Al2O3, Fe, Ni, or Cu), an intermediate layer (Ir, MgO, YSZ, SrTiO3, or Ru), and the diamond layer. This segmentation allows each component to serve its specific function - the initial substrate provides mechanical support and thermal conductivity, the intermediate layer provides lattice matching, and the diamond layer provides the desired crystal quality with large area coverage
Solution Approach 2:
The intermediate layer acts as a mediator between the initial substrate and the diamond layer. It has a lattice constant specifically suited for both the initial substrate and diamond, reducing lattice mismatch and enabling high-quality diamond growth over large areas while maintaining single crystal structure
2Area of stationary object
If CVD method is used on polycrystal diamonds, then large area (6 inches diameter) with high purity is achieved, but single crystallization is difficult due to large lattice constant difference
Solution Approach 1:
The intermediate layer serves as a lattice-matched intermediary that enables single crystal diamond growth on large-area substrates. By selecting materials with appropriate lattice constants (Ir: 3.84 Å, MgO: 4.21 Å, YSZ: 5.12 Å, SrTiO3: 3.91 Å, Ru: 2.71 Å), the system bridges the gap between the initial substrate and diamond, allowing CVD method to produce large-area single crystal diamond that would otherwise be impossible
Solution Approach 2:
The invention changes the lattice parameter matching condition by introducing an intermediate layer with specific lattice constants. This parameter change enables the system to overcome the 34.3% lattice mismatch between diamond and Si, allowing heteroepitaxial growth of single crystal diamond on large substrates with controlled crystal orientation
3Area of stationary object
If mosaic method is used to join multiple HPHT substrates, then larger area is achieved, but joint imperfections remain
Solution Approach 1:
The invention avoids the mosaic method's jointing problem by segmenting the system into functionally distinct layers. Instead of joining multiple diamond substrates together, it grows a continuous diamond layer on a segmented initial substrate+intermediate layer structure, eliminating joint imperfections while achieving large area coverage
4Area of stationary object
If heteroepitaxial growth is attempted on Si substrate, then large area growth is possible, but 34.3% lattice constant difference causes growth difficulty
Solution Approach 1:
The intermediate layer acts as a lattice-matched intermediary that enables single crystal diamond growth on large-area substrates. By selecting materials with appropriate lattice constants (Ir: 3.84 Å, MgO: 4.21 Å, YSZ: 5.12 Å, SrTiO3: 3.91 Å, Ru: 2.71 Å), the system bridges the gap between the initial substrate and diamond, allowing CVD method to produce large-area single crystal diamond that would otherwise be impossible
Solution Approach 2:
The invention changes the lattice parameter matching condition by introducing an intermediate layer with specific lattice constants. This parameter change enables the system to overcome the 34.3% lattice mismatch between diamond and Si, allowing heteroepitaxial growth of single crystal diamond on large substrates with controlled crystal orientation
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 approach results in single crystal diamond substrates with improved crystallinity, reduced defects, and high quality, suitable for electronic and magnetic devices, while also allowing for the production 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
growing the diamond nucleus formed on the intermediate layer to perform epitaxial growth, thereby forming a single crystal diamond layer
Implementation Method 3
a vapor deposition (Chemical Vapor Deposition: CVD) method can provide large-area diamonds
Data Source
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AI summary
The present invention is an underlying substrate for a single crystal diamond laminate substrate including 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.