Single-Crystal Substrate Warpage for Group-III Nitride Crack Prevention
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Solution Overview
Problem
Existing methods for growing Group-III nitride crystals face challenges in achieving large area and thick film thickness due to crystal cracking, despite techniques regulating base substrate warpage and surface shape, which are insufficient in preventing cracking.
Innovation Solution
A single-crystal substrate with a specific relationship between physical and crystallographic-plane shape warpage, where the amount of warpage of the physical shape (Z1) and the crystallographic-plane shape (Z2) are optimized to inhibit cracking, allowing for the growth of large area and thick films without defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a film is grown to a thickness of several tens of micrometers to several hundred micrometers or more on a base substrate, then a thick Group-III element nitride semiconductor layer can be obtained, but cracks generate in the crystal during the growth
Solution Approach 1:
The invention changes the warpage parameters of the base substrate by specifying a radius of curvature of 2 m or more. This parameter adjustment prevents the generation of cracks during thick film growth while maintaining the ability to produce large-area crystals. The controlled warpage compensates for thermal stress and lattice mismatch that would otherwise cause cracking in thick films.
Solution Approach 2:
The invention applies curvature to the base substrate surface by regulating its warpage to have a radius of curvature of 2 m or more. This curved surface configuration reduces stress concentration and prevents crack formation during the growth of thick Group-III element nitride semiconductor films, enabling reliable production of large-area, thick-film substrates.
2Manufacturing precision
If a single-crystal gallium nitride substrate is obtained by growing single-crystal gallium nitride having a thickness of about 500 μm to 1 mm on one base substrate, then a desired substrate can be obtained, but the production efficiency is exceedingly low
Solution Approach 1:
The invention enables segmentation of a single large-area, thick-film crystal into multiple substrates. By growing a large-area crystal (e.g., 100 mm diameter) to sufficient thickness on a warpage-regulated base substrate, the crystal can be sliced into multiple individual substrates, thereby increasing production efficiency while maintaining single-crystal quality.
Solution Approach 2:
The invention performs preliminary action by regulating the base substrate warpage before crystal growth. This pre-conditioning of the substrate prevents crack formation during growth, ensuring that the entire large-area crystal can be grown without defects, which is a prerequisite for subsequent slicing into multiple substrates.
3Reliability
If the shape of the base substrate is regulated to inhibit crystal cracking, then crystal quality can be improved, but the substrate complexity increases
Solution Approach 1:
The invention simplifies the substrate configuration by specifying a clear parameter (radius of curvature ≥ 2 m) for warpage regulation. This quantitative parameter provides a straightforward manufacturing criterion that balances crack prevention with manufacturing simplicity, avoiding overly complex substrate designs while achieving reliable crack-free growth.
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 optimized substrate configuration enables stable production of Group-III nitride crystals with large thickness and area, improving productivity and yielding high-quality light-emitting semiconductor elements or devices.
Implementation Method 1
the amount of warpage of the physical shape (Z1) and the amount of warpage of the crystallographic-plane shape (Z2) satisfy the following expression (1): |Z1+Z2|<0.06×(X/Y)2
Implementation Method 2
a Group-III element nitride semiconductor substrate can be produced by using vapor phase growth methods such as a hydride vapor phase epitaxy (HVPE) method and a metal-organic chemical vapor deposition (MOCVD) method
Implementation Method 3
Gases for Group-III element nitride semiconductor formation which include, for example, a gas containing a gallium compound and a gas containing a nitrogen compound are fed to the inside of the reactor to thereby grow a gallium nitride semiconductor
Data Source
Figure 1(a)~1(e)
Figure 2~3(d)
Figure 4
AI summary
Provided is a base substrate with which a Group-III nitride crystal having a large area and a large thickness can be grown while inhibiting crack generation. A single-crystal substrate for use in growing a Group-III nitride crystal thereon, which satisfies the following expression (1), wherein Z1 (µm) is an amount of warpage of physical shape in a growth surface of the single-crystal substrate and Z2 (µm) is an amount of warpage calculated from a radius of curvature of crystallographic-plane shape in a growth surface of the single-crystal substrate: -40<Z2/Z1<-1 : Expression (1).