HVPE Group III Nitride Substrate Growth on Matched Thermal Expansion Base
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Solution Overview
Problem
Current methods for producing large-sized, high-quality GaN-based or AlN-based substrates face challenges such as warpage, lattice defects, and high costs due to difficulties in growing large crystals and maintaining crystal orientation and planarity, especially with mismatched lattice constants and thermal expansion coefficients between substrate materials.
Innovation Solution
A method involving a vapor phase synthesis for forming a group III nitride base substrate, followed by a hydride vapor phase epitaxy to grow a group III compound crystal on a seed substrate, using materials like Si, sapphire, or GaAs, with a focus on controlling thermal expansion and impurity diffusion through techniques like thin film transfer and N-face group III nitride layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a plurality of tile-shaped substrates are bonded on a pyrolytic graphite susceptor to enlarge the GaN single crystal, then the substrate size is increased, but the seed substrate moves, peels, warps, or loses crystal orientation due to large difference in coefficient of thermal expansion between the PG susceptor, adhesive, and GaN crystal
Solution Approach 1:
The patent changes the material parameter (coefficient of thermal expansion) of the base substrate by selecting a material whose thermal expansion coefficient closely matches that of GaN (e.g., AlN, SiC, or specific ceramic compositions). This parameter matching prevents thermal stress-induced warpage and maintains crystal orientation during high-temperature epitaxial growth, resolving the contradiction between substrate size enlargement and manufacturing precision.
Solution Approach 2:
The patent introduces an intermediate layer between the seed substrate and the base substrate. This intermediate layer acts as a buffer that accommodates thermal expansion differences and prevents direct stress transmission, thereby maintaining crystal orientation and planarity while allowing large-area substrates to be processed without warpage or peeling.
2Manufacturing precision
If single crystal substrates with same or close lattice constant and thermal expansion coefficient to GaN are used, then crystal quality is improved, but the substrate size remains small because large single crystal substrates are not currently manufactured
Solution Approach 1:
The patent segments the base substrate into a reusable support structure that is distinct from the GaN crystal layer. The GaN crystal is grown as a separate layer on the base substrate, allowing the base substrate to be reused for multiple growth cycles. This segmentation enables production of large-area GaN substrates even when large single crystals are not commercially available, while maintaining high crystal quality through controlled epitaxial growth.
Solution Approach 2:
The patent performs preliminary preparation of the base substrate surface (e.g., polishing, cleaning, or forming a buffer layer) before epitaxial growth to ensure optimal conditions for high-quality GaN crystal formation. This preliminary action on the base substrate enables subsequent growth of large-area, high-quality GaN substrates without requiring pre-existing large single crystals.
3Area of stationary object
If GaN is heteroepitaxially grown or homoepitaxially grown on single-crystal substrates by MOCVD or HVPE method, then large-sized substrate can be produced in principle, but various defects increase due to large mismatch in lattice constant and thermal expansion coefficient
Solution Approach 1:
The patent optimizes the physical and chemical parameters of the base substrate, specifically selecting materials with lattice constants and thermal expansion coefficients that closely match GaN (e.g., AlN with similar thermal expansion, SiC with compatible lattice structure). This parameter matching dramatically reduces dislocation density and other defects during epitaxial growth, enabling production of large-area, high-quality GaN substrates.
Solution Approach 2:
The patent employs composite structures consisting of a base substrate (e.g., AlN, SiC, or ceramic composite) combined with epitaxially grown GaN layers. The base substrate provides mechanical support and thermal management, while the GaN layer provides the desired semiconductor properties. This composite approach enables large-area substrates with low defect densities by decoupling the requirements for mechanical strength and crystal 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
This method enables the production of large-sized, high-quality group III compound substrates with minimal warpage and lattice defects at a lower cost, leveraging the high film formation rate of hydride vapor phase epitaxy while ensuring purity and crystal quality.
Implementation Method 1
forming a group III compound crystal on the seed substrate by a hydride vapor phase epitaxy method
Implementation Method 2
forming a group III compound crystal on the seed substrate by a hydride vapor phase epitaxy method
Implementation Method 3
forming a group III nitride base substrate by a vapor phase synthesis method
Data Source
AI summary
The present invention relates to a method for producing a group III compound substrate, including: a base substrate forming step for forming a group III nitride base substrate by a vapor phase synthesis method; a seed substrate forming step for forming a seed substrate on the base substrate; and a group III compound crystal forming step for forming a group III compound crystal on the seed substrate by a hydride vapor phase epitaxy method. The group III compound substrate of the present invention is produced by the method for producing a group III compound substrate of the present invention. According to the present invention, a large-sized and high-quality group III compound substrate can be obtained at a low cost while taking advantage of the high film formation rate characteristic of the hydride vapor phase epitaxy method.