Semiconductor Substrate Lattice Mismatch Reduction
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Solution Overview
Problem
Existing semiconductor substrates face challenges in achieving high epitaxial quality due to high threading dislocation densities and crystallographic defects, particularly when growing layers with significantly different lattice constants, which affects the performance of devices like LEDs and transistors.
Innovation Solution
A semiconductor substrate is designed with a first semiconductor layer and a second semiconductor layer, where the lattice constant difference is greater than 3.6%, and the second layer is grown epitaxially on a growth substrate with a different crystal structure, reducing threading dislocations and improving surface roughness through precise epitaxial growth techniques like MOCVD or HVPE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a second semiconductor layer with a significantly different lattice constant is grown on a first semiconductor layer, then the device can achieve different functional properties, but high threading dislocation density and crystallographic defects occur
Solution Approach 1:
The patent introduces an intermediate layer between the first and second semiconductor layers. This intermediate layer has a lattice constant that gradually transitions from the first layer to the second layer, acting as a mediator that reduces the abrupt lattice mismatch. The intermediate layer absorbs the stress and prevents threading dislocations from propagating through the structure, thereby enabling the use of materials with significantly different lattice constants while maintaining device reliability.
Solution Approach 2:
The patent employs parameter changes by carefully controlling the composition and thickness of the intermediate layer. By adjusting the lattice constant parameter of the intermediate layer to be between that of the first and second semiconductor layers, the patent creates a gradual transition zone. This parameter optimization reduces the lattice mismatch stress and minimizes threading dislocation density, allowing versatile device design with different material combinations.
2Adaptability or versatility
If epitaxial growth is performed with large lattice mismatch, then material composition flexibility increases, but manufacturing precision deteriorates due to surface roughness and defects
Solution Approach 1:
The intermediate layer serves as a mediator that enables the growth of materials with large lattice mismatches while maintaining high epitaxial quality. By placing this intermediate layer between the substrate and the target layer, the patent creates a transition zone that accommodates the lattice mismatch, preventing surface roughness and crystallographic defects that would otherwise occur during epitaxial growth of mismatched materials.
Solution Approach 2:
The patent utilizes parameter changes in the intermediate layer's composition and thickness to optimize the epitaxial growth process. By controlling the lattice constant parameter of the intermediate layer to fall between that of the substrate and the second semiconductor layer, the patent achieves gradual lattice transition. This parameter optimization maintains manufacturing precision while allowing flexibility in material composition selection for device fabrication.
3Ease of manufacture
If conventional growth methods are used for layers with different crystal structures, then process simplicity is maintained, but device performance suffers due to high defect density
Solution Approach 1:
The patent introduces an intermediate layer as a mediator between conventional growth methods and high-performance requirements. This intermediate layer can be grown using standard epitaxial techniques, maintaining process simplicity, while its specific lattice constant properties prevent threading dislocation formation. The intermediate layer thus bridges the gap between easy manufacturing and high device performance by enabling the growth of layers with different crystal structures without sacrificing reliability.
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 results in a semiconductor substrate with reduced threading dislocation density and improved epitaxial quality, enhancing the performance and reliability of devices such as LEDs and transistors by minimizing crystallographic defects and surface roughness.
Implementation Method 1
A second semiconductor layer is epitaxially grown on the growth substrate, and the semiconductor layer has a second lattice constant (L2)
Data Source
AI summary
A semiconductor substrate is provided in the present disclosure. The semiconductor substrate includes a first semiconductor layer and a second semiconductor layer on the first semiconductor layer. The first semiconductor layer has a first lattice constant (L1) and the second semiconductor layer has a second lattice constant (L2). A ratio of a difference (L2-L1) between the second lattice constant (L2) and the first lattice constant (L1) to the first lattice constant (L1) is greater than 0.036.