Ga2O3 Single-Crystal Substrate Warpage Control for Crack-Free Epitaxy
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Solution Overview
Problem
Ga2O3-based single crystal substrates exhibit strong cleavability due to their monoclinic crystal system, leading to cracks and delamination when AlxGa(1-x)N-based semiconductors are laminated, complicating the semiconductor lamination process and preventing the production of high-quality, homogeneous semiconductor films.
Innovation Solution
A Ga2O3-based single crystal substrate with controlled warpage, surface orientation, and dopant concentrations is developed, allowing for the growth of AlxGa(1-x)N-based semiconductor layers without cracks or delamination, using an induction heating method for crystal growth and precise substrate processing to achieve low dislocation density and surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Ga2O3-based single crystal substrate with monoclinic crystal system is used, then new crystal system with low symmetry is achieved, but very strong cleavability occurs leading to cracks and delamination
Solution Approach 1:
The patent changes the crystal growth parameters including temperature gradient, pulling speed, and composition ratio to control the crystal structure and reduce cleavability. By optimizing these parameters, the substrate maintains structural integrity while preserving the monoclinic crystal system's unique properties
Solution Approach 2:
The patent creates a composite structure by laminating AlxGa(1-x)N-based semiconductor layers on Ga2O3-based single crystal substrate with controlled composition and structure. This composite approach allows the substrate to provide mechanical stability while the semiconductor layer provides functional properties
2Adaptability or versatility
If AlxGa(1-x)N-based semiconductor layer is laminated on Ga2O3-based single crystal substrate, then semiconductor device fabrication is enabled, but thermal expansion coefficient and lattice constant mismatch causes warpage and cracking
Solution Approach 1:
The patent introduces an AlN buffer layer as an intermediary between the Ga2O3 substrate and AlxGa(1-x)N semiconductor layer. This buffer layer has lattice constant and thermal expansion coefficient intermediate between the substrate and semiconductor, reducing mismatch stress and preventing warpage and cracking
Solution Approach 2:
The patent optimizes the composition ratio x in AlxGa(1-x)N and the thickness of the buffer layer to control thermal expansion and lattice matching. By carefully adjusting these parameters, the patent achieves stress-free lamination and high-quality semiconductor films
3Reliability
If interface resistance reduction layer and stress alleviating layer are added, then crack occurrence is reduced, but lamination process becomes complicated
Solution Approach 1:
The patent combines the functions of interface resistance reduction and stress alleviation into a single AlN buffer layer. This merged layer simultaneously provides low interface resistance and stress management, eliminating the need for separate layers and simplifying the overall lamination process
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 approach enables the production of high-quality, homogeneous AlxGa(1-x)N-based semiconductor films, improving the yield and productivity of UV LEDs and power semiconductor devices by eliminating cracks and delamination, and allowing for large-scale substrate manufacturing.
Implementation Method 1
using an induction heating method for crystal growth
Implementation Method 2
since a thermal expansion coefficient and/or a lattice constant of the Ga2O3-based single crystal substrate are different from those of the AlxGa(1-x)N-based semiconductor layer, the AlxGa(1-x)N-based semiconductor layer and the Ga2O3-based single crystal substrate warp
Data Source
AI summary
The Ga2O3-based single crystal substrate has an amount of warpage of −50 μm or more and 50 μm or less (including 0 μm) on a main surface. The method of manufacturing a Ga2O3-based single crystal substrate includes processing a substrate from a Ga2O3-based single crystal grown according to an induction heating type single crystal growth method to have an amount of warpage of −50 μm or more and 50 μm or less (including 0 μm) on a main surface.