Single-Crystal Diamond Growth Base Material with MgO Buffer Layer
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Solution Overview
Problem
Current methods for growing single-crystal diamond substrates face challenges in achieving large area and high crystallinity while maintaining cost-effectiveness, as existing techniques either suffer from high costs, stress-induced breakage, or compromised crystallinity due to thermal expansion mismatch and separation difficulties.
Innovation Solution
A single-crystal diamond growth base material comprising a base substrate with a linear expansion coefficient similar to diamond, a high-crystallinity MgO layer, and a heteroepitaxially grown iridium, rhodium, or platinum film, which acts as a buffer layer to reduce thermal stress and facilitate high-quality diamond growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If homoepitaxial CVD single-crystal diamond is grown directly on an HPHT single-crystal diamond base material, then the base material and grown diamond are difficult to separate, but this increases cost and requires ion implantation or prolonged wet etching
Solution Approach 1:
The patent introduces an intermediate MgO layer between the HPHT diamond base material and the CVD-grown diamond, creating distinct segments that facilitate separation. The MgO layer acts as a buffer zone with different material properties, allowing the grown diamond to be separated from the base material through selective etching of the MgO layer without damaging the diamond crystals.
Solution Approach 2:
The MgO layer serves as an intermediary substance between the HPHT diamond base material and the CVD-grown diamond. This intermediate layer has specific properties that enable both good epitaxial growth of diamond and easy separation from the base material, resolving the contradiction between maintaining crystallinity and enabling separation.
2Ease of manufacture
If ion implantation is performed on the base material to enable separation, then separation becomes possible, but the crystallinity of the obtained single-crystal diamond is lowered
Solution Approach 1:
The MgO layer is introduced in advance during the base material preparation stage, before the CVD diamond growth process. This preliminary action of creating the MgO buffer layer enables separation without requiring ion implantation during or after growth, thereby preserving the crystallinity of the grown diamond while still achieving separation capability.
3Area of stationary object
If CVD single-crystal diamond is grown on a single-crystal Ir film on single-crystal MgO base material, then large area growth is possible, but stress causes the base material and grown diamond to break into pieces
Solution Approach 1:
The patent modifies the thermal expansion parameter by selecting a base material with thermal expansion coefficient matching that of diamond. This parameter change reduces thermal stress during the CVD growth process, preventing the base material and grown diamond from breaking into pieces while still enabling large area growth.
Solution Approach 2:
The patent applies different material properties to different layers: the base material has thermal expansion matched to diamond, while the MgO layer provides chemical separation capability. This local differentiation of material qualities allows simultaneous achievement of stress resistance and separation capability.
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 growth of large-area single-crystal diamond substrates with excellent crystallinity at a lower cost, reducing stress and enabling easy separation, thus overcoming the limitations of existing methods.
Implementation Method 1
a base substrate consisting of a material having a linear expansion coefficient smaller than that of MgO and not smaller than 0.5×10−6/K
Implementation Method 2
a film constituted of any one of an iridium film, a rhodium film, and a platinum film heteroepitaxially grown on the single-crystal MgO layer
Implementation Method 3
CVD single-crystal diamond heteroepitaxially grown by a CVD method on an single-crystal iridium (Ir) film heteroepitaxially grown on a single-crystal MgO base material
Data Source
AI summary
A single-crystal diamond growth base material on which single-crystal diamond is grown having at least a base substrate of a material having a linear expansion coefficient smaller than that of MgO and not smaller than 0.5×10−6/K; a single-crystal MgO layer formed on a face of the base substrate where the single-crystal diamond is grown by a bonding method; and a film constituted of any one of an iridium film, a rhodium film, and a platinum film heteroepitaxially grown on the single-crystal MgO layer.