Engineered Ceramic Substrate Structure for Uniform GaN Epitaxy
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Solution Overview
Problem
The heteroepitaxial growth of gallium nitride based LED structures on sapphire substrates leads to reduced uniformity and adverse effects on the electronic/optical properties of the epitaxial layers, necessitating improved methods and systems for epitaxial growth processes.
Innovation Solution
The development of an engineered substrate structure with a coefficient of thermal expansion (CTE) matched to epitaxial layers, comprising a polycrystalline ceramic core, adhesion layers, a conductive layer, and a barrier layer, which simplifies process integration and enhances the match with gallium nitride-based epitaxial and device layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If heteroepitaxial growth is used to grow gallium nitride based LED structures on sapphire substrates, then LED devices can be manufactured, but the uniformity of the epitaxial layers is reduced and electronic/optical properties deteriorate
Solution Approach 1:
The patent introduces an intermediary layer (buffer layer) between the sapphire substrate and the gallium nitride epitaxial layers. This buffer layer acts as a mediator that reduces the lattice mismatch and thermal expansion coefficient difference between the substrate and the epitaxial material, thereby improving uniformity and electronic/optical properties while enabling heteroepitaxial growth to proceed
Solution Approach 2:
The patent employs a composite substrate structure consisting of multiple materials (sapphire substrate, buffer layer, and potentially other intermediate layers) with carefully selected properties. This composite approach allows optimization of both mechanical compatibility (CTE matching) and crystallographic compatibility (lattice matching) to resolve the contradiction between manufacturability and quality
2Ease of manufacture
If sapphire substrates are used for heteroepitaxial growth, then LED manufacturing is enabled, but adverse effects occur on the electronic and optical properties of the epitaxial layers
Solution Approach 1:
The buffer layer serves as an intermediary that decouples the direct interaction between the sapphire substrate and the gallium nitride epitaxial layers. This intermediary structure enables the use of sapphire substrates (which have advantages for manufacturing) while preventing the direct adverse effects on electronic and optical properties by providing a transition zone with graded properties
3Productivity
If heteroepitaxial growth process is employed, then gallium nitride based LED structures can be produced, but reduced uniformity and adverse effects occur
Solution Approach 1:
The buffer layer is prepared in advance (preliminary action) before the actual growth of the gallium nitride LED structures. This preliminary layer preparation establishes favorable growth conditions upfront, preventing uniformity issues during subsequent production and enabling high-volume manufacturing without sacrificing quality
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 engineered substrate structure achieves improved uniformity and enhanced electronic/optical properties by matching the CTE of the substrate with the epitaxial layers, while the encapsulating layers prevent impurity diffusion, leading to optimized performance in optical, electronic, and optoelectronic applications.
Implementation Method 1
Encapsulating layers utilized as components of the engineered substrate structure block diffusion of impurities present in central portions of the substrate from reaching the semiconductor processing environment
Implementation Method 2
a silicon oxide layer coupled to the support structure, a substantially single crystalline silicon layer coupled to the silicon oxide layer
Data Source
AI summary
A substrate includes a support structure comprising a polycrystalline ceramic core, a first adhesion layer encapsulating the polycrystalline ceramic core, a barrier layer encapsulating the first adhesion layer, a second adhesion layer coupled to the barrier layer, and a conductive layer coupled to the second adhesion layer. The substrate also includes a bonding layer coupled to the support structure, a substantially single crystal silicon layer coupled to the bonding layer, and an epitaxial semiconductor layer coupled to the substantially single crystal silicon layer.