Multi-Deposition GaN Epitaxy for Thermal Stress Reduction
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Solution Overview
Problem
Wide band gap semiconductor devices, particularly gallium nitride (GaN) devices, face challenges due to lattice mismatch and different coefficients of thermal expansion between GaN layers and carrier substrates, leading to defects, strains, and high manufacturing costs, limiting their scalability and integration capabilities.
Innovation Solution
The use of engineered substrates with matched coefficients of thermal expansion, combined with metalorganic chemical vapor deposition (MOCVD) and hybrid vapor phase epitaxy (HVPE) processes, allows for the growth of thick, high-quality GaN epitaxial layers on larger substrates, reducing dislocation density and enabling larger wafer sizes and more complex circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If GaN is deposited on a semiconductor carrier substrate with different lattice structure, then GaN epitaxial growth can be achieved, but defects, dislocations, and strains are created that negatively impact device yields and performance
Solution Approach 1:
The patent introduces an intermediary buffer layer structure between the carrier substrate and the GaN epitaxial layer. This buffer layer acts as a mediator that gradually transitions the lattice mismatch, reducing dislocation density and improving the quality of the GaN layer without requiring a perfect lattice match substrate.
Solution Approach 2:
The patent segments the GaN epitaxial growth into multiple stages with different deposition conditions. By dividing the growth process into distinct phases (nucleation, initial growth, mature growth), each optimized for specific parameters, the overall layer quality is improved while minimizing defect propagation from the substrate interface.
2Ease of manufacture
If thermal processing is performed for GaN epitaxial growth, then GaN layers can be formed, but cracking, delamination, or substrate breakage occurs due to different coefficients of thermal expansion
Solution Approach 1:
The patent modifies the thermal processing parameters including heating rate, peak temperature, and cooling rate to minimize thermal stress. By carefully controlling these parameters and using a multi-stage thermal profile, the patent achieves successful GaN epitaxial growth while preventing substrate cracking and delamination caused by thermal expansion mismatch.
3Ease of manufacture
If conventional deposition processes are used, then manufacturing is simpler, but thick enough epitaxial layers cannot be formed to support various electronics applications
Solution Approach 1:
The patent employs continuous epitaxial growth processes that maintain optimal deposition conditions throughout the entire growth duration. By ensuring continuous supply of precursors, maintaining stable temperature and pressure profiles, and preventing interruptions, the patent achieves thick epitaxial layers with consistent quality that support complex electronic applications.
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 GaN devices with lower dislocation density and higher performance, enabling larger wafer diameters and thicker epitaxial layers, which reduce manufacturing costs and facilitate more complex integrated circuitry, while maintaining thermal expansion matching over a wide temperature range.
Implementation Method 1
depositing a first GaN-based epitaxial layer coupled to the engineered substrate using a metalorganic chemical vapor deposition (MOCVD) process
Implementation Method 2
depositing a second GaN-based epitaxial layer coupled to the first GaN-based epitaxial layer using a hybrid vapor phase epitaxy (HVPE) deposition process
Data Source
AI summary
A group III-nitride (III-N)-based electronic device includes an engineered substrate, a metalorganic chemical vapor deposition (MOCVD) III-N-based epitaxial layer coupled to the engineered substrate, and a hybrid vapor phase epitaxy (HVPE) III-N-based epitaxial layer coupled to the MOCVD epitaxial layer.