Group III-V Superlattice Base Structure to Reduce Epitaxial Dislocations
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Solution Overview
Problem
The mismatch between Group IV based substrates and Group III-V based epitaxial structures, particularly due to lattice and thermal expansion coefficient mismatches, leads to dislocations, reduced device performance, and cracking during the growth of Group III-V based epitaxial structures on Group IV based substrates.
Innovation Solution
A base structure is introduced with a Group III-V superlattice layer comprising multiple lattice stack layers, where the proportion of the first Group III component decreases away from the substrate, facilitating structural and stress relaxation, and an epitaxial structure is formed on this layer to improve the quality and reduce dislocations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Group III-V based epitaxial structure is grown on Group IV based substrate, then low cost and high thermal conductivity are achieved, but lattice mismatch and thermal expansion coefficient mismatch cause dislocations and reduced device performance
Solution Approach 1:
A Group III-V superlattice layer is introduced as an intermediary between the Group IV substrate and the Group III-V epitaxial structure. This superlattice layer comprises multiple lattice stack layers with gradually varying composition gradients, serving as a transition zone that mediates the lattice mismatch and thermal expansion coefficient difference between the substrate and epitaxial structure, thereby reducing dislocation density and improving device performance
Solution Approach 2:
The patent employs parameter changes by creating a gradient in the composition of the Group III-V superlattice layer. The proportion of the first Group III component varies across different semiconductor layers within the superlattice, transitioning from higher proportion near the substrate to lower proportion near the epitaxial structure. This gradual parameter change enables continuous lattice constant adjustment, facilitating smooth transition and reducing abrupt mismatches
2Ease of manufacture
If Group III-V based epitaxial structure is grown on Group IV based substrate, then manufacturing simplicity is maintained, but thermal expansion coefficient mismatch causes cracking during cooling process
Solution Approach 1:
The Group III-V superlattice layer implements parameter changes through composition gradient, where the proportion of the first Group III component gradually decreases from the substrate side toward the epitaxial structure side. This continuous parameter variation enables progressive thermal expansion coefficient adjustment, allowing the structure to accommodate thermal stress during cooling without sudden cracking, while maintaining manufacturing simplicity
Solution Approach 2:
The Group III-V superlattice layer acts as a pre-designed cushioning structure that anticipates and absorbs thermal stress before it can cause cracking in the epitaxial structure. The gradient composition is engineered beforehand to provide progressive stress relaxation, protecting the epitaxial structure from thermal shock during the cooling process
3Reliability
If conventional epitaxial growth is used, then manufacturing process is simple, but high dislocation density reduces device performance
Solution Approach 1:
The patent segments the transition zone into multiple lattice stack layers, where each layer contains at least two semiconductor layers with different compositions. This segmentation creates a stepped gradient structure that progressively manages lattice mismatch, distributing dislocation formation across multiple interfaces rather than allowing a single abrupt mismatch, thereby reducing overall dislocation density
Solution Approach 2:
The invention implements parameter changes by systematically varying the proportion of the first Group III component across different semiconductor layers in the superlattice. This controlled parameter variation creates a gradient in lattice constants that gradually bridges the mismatch between substrate and epitaxial structure, significantly reducing dislocation density and improving manufacturing precision
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 Group III-V superlattice layer effectively reduces dislocation density, minimizes cracking, and enhances the performance and service life of the semiconductor device by providing structural and stress relaxation during the cooling process.
Implementation Method 1
a growth of a Group III-V based epitaxial structure on a Group IV based substrate is prone to cause mismatch problems
Implementation Method 2
mismatch problems... leads to dislocations, reduced device performance, and cracking during the growth of Group III-V based epitaxial structures
Data Source
AI summary
A base structure and a method for manufacturing the base structure, and a semiconductor device are provided. The base structure includes a substrate and a Group III-V superlattice layer. The Group III-V superlattice layer includes a plurality of lattice stack layers stacked on the substrate. A lattice stack layer includes at least two semiconductor layers, and a semiconductor layer includes a first Group III component and a second Group III component. In a same lattice stack layer, a proportion of the first Group III component in a semiconductor layer away from the substrate is less than a proportion of the first Group III component in a semiconductor layer proximate to the substrate. The Group III-V superlattice layer can effectively achieve structural relaxation between the substrate and an epitaxial structure, reduce dislocation density in the epitaxial structure and improve a performance of a device manufactured on the epitaxial structure.