GaN Seeded Composite Substrate for Low-Warp Nitride Epitaxy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing nitride semiconductor substrates face challenges such as warp generation, dislocation formation, and limited thickness due to differences in thermal expansion coefficients and lattice constants, which affect the crystallinity and reliability of GaN epitaxial layers.
Innovation Solution
A nitride semiconductor substrate is developed with a group III-nitride semiconductor layer formed on a support substrate that includes a composite substrate with laminated layers and a group III-nitride semiconductor seed crystal layer. The seed crystal layer has excellent crystallinity, with a crystallinity of 550 arcsec or less in XRD half-value width, which reduces dislocation density and improves crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a silicon single-crystal substrate is used for GaN epitaxial growth, then the substrate is inexpensive and suitable for large diameter enlargement, but thermal expansion coefficient mismatch causes stress and cracks during cooling, limiting the crack-free thickness to about 5 μm
Solution Approach 1:
The patent introduces a buffer layer between the silicon substrate and the GaN epitaxial layer. This buffer layer acts as an intermediary that accommodates the thermal expansion coefficient mismatch, reducing stress and preventing cracks from propagating through the entire structure, thereby enabling thicker crack-free GaN layers while maintaining the advantages of silicon substrates
Solution Approach 2:
The patent creates a composite structure consisting of multiple layers (silicon substrate, buffer layer, and GaN epitaxial layer) with different material properties. This composite approach allows each layer to perform its specific function: the silicon substrate provides mechanical support and thermal management, the buffer layer manages stress, and the GaN layer provides the desired semiconductor properties
2Reliability
If a GaN substrate is used for epitaxial growth, then warp and dislocation issues are eliminated due to matching thermal expansion coefficient and lattice constant, but the substrate is difficult to produce and very expensive with limited diameter
Solution Approach 1:
The buffer layer serves as an intermediary that enables the use of inexpensive silicon substrates while achieving crystallinity comparable to GaN-on-GaN structures. The buffer layer compensates for the lattice mismatch between silicon and GaN, allowing high-quality GaN growth without requiring expensive GaN substrates
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 substrate achieves a group III-nitride semiconductor layer with low dislocation density and excellent crystallinity, reducing warp and crack issues during epitaxial growth, and enabling the formation of thick, crack-free layers.
Implementation Method 1
a group III-nitride semiconductor layer containing GaN and formed on a support substrate
Implementation Method 2
a support substrate for GaN, or simply a growth substrate) has been developed. A general support substrate for GaN is constituted with: a support structure including a polycrystalline ceramic core
Data Source
AI summary
The present invention is a nitride semiconductor substrate including a group III-nitride semiconductor layer containing GaN and formed on a support substrate, in which the support substrate includes: a composite substrate having laminated layers, the laminated layers including a polycrystalline ceramic core, a first adhesive layer bonded entirely to the polycrystalline ceramic core, a second adhesive layer laminated entirely to the first adhesive layer, and a barrier layer bonded entirely to the second adhesive layer; and a group III-nitride semiconductor seed crystal layer containing at least GaN, bonded on the composite substrate via a planarization layer, in which the group III-nitride semiconductor layer is formed on the group III-nitride semiconductor seed crystal layer, and crystallinity on a (0002) growth surface of GaN in the group III-nitride semiconductor seed crystal layer is 550 arcsec or less in XRD half-value width. This can provide the nitride semiconductor substrate, including the group III-nitride semiconductor layer, with a small warp, low generation of dislocation, and excellent crystallinity.