GaN Substrate Fabrication via Voided Nitride Embedding Layer
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Solution Overview
Problem
The challenge in fabricating gallium nitride (GaN) substrates lies in the occurrence of bending and cracks due to stress between the base substrate and the GaN thick film, particularly when grown on sapphire substrates, which complicates the process and increases costs and time, and existing solutions either use expensive materials or require complex masking processes.
Innovation Solution
A method involving the growth of a nitride embedding layer with indium-rich parts between the GaN layer and the base substrate, where the indium-rich parts are metallized to form voids at a higher temperature, mitigating stress and reducing bending and cracking by creating a voided structure that relieves strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a sapphire substrate is used to grow GaN film, then the film quality can be maintained due to hexagonal system compatibility, but stress and bending occur due to lattice constant and thermal expansion coefficient differences
Solution Approach 1:
The patent introduces an intermediate layer between the sapphire substrate and GaN film, segmenting the direct contact interface into two separate interfaces. This intermediate layer has lattice constants and thermal expansion coefficients intermediate between sapphire and GaN, thereby reducing the overall mismatch stress and preventing bending and cracks while maintaining film quality.
Solution Approach 2:
The patent employs an intermediate layer as a mediator between the sapphire substrate and GaN film. This intermediate layer acts as a buffer that reduces the thermal expansion coefficient difference and lattice constant mismatch, preventing stress transfer and bending while allowing high-quality GaN film growth.
2Length of stationary object
If GaN thick film is grown on sapphire substrate, then sufficient thickness can be achieved, but bending and cracks occur due to stress transfer
Solution Approach 1:
The patent segments the stress path by introducing an intermediate layer between the sapphire substrate and GaN thick film. This allows the GaN film to reach sufficient thickness for substrate-free operation while the intermediate layer absorbs and distributes the stress, preventing bending and cracks from developing.
Solution Approach 2:
The patent changes the thermal expansion coefficient parameter by introducing an intermediate layer with intermediate thermal expansion properties. This parameter change allows the system to accommodate the thermal stress that would otherwise cause bending and cracks in thick GaN films grown directly on sapphire substrates.
3Reliability
If mask or oxide embedding layer is used to prevent bending, then stress can be reduced, but the fabrication process becomes complicated and costly
Solution Approach 1:
The patent merges the functions of the intermediate layer into a single layer that simultaneously addresses lattice mismatch, thermal expansion coefficient difference, and stress reduction. This eliminates the need for separate mask layers or oxide embedding layers, simplifying the fabrication process while maintaining bending prevention.
Solution Approach 2:
The intermediate layer serves multiple functions: it acts as a buffer for lattice constant mismatch, a thermal expansion coefficient buffer, and a stress distribution layer. This multi-functionality replaces the need for multiple separate layers (mask, oxide embedding), reducing fabrication complexity and cost.
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 simplifies the fabrication process, reduces manufacturing costs and time, and enables the production of high-quality GaN substrates without cracks by effectively managing stress between the GaN layer and the base substrate through the formation of voids in the nitride embedding layer.
Implementation Method 1
applying a second temperature higher than the first temperature to the nitride embedding layer so that the indium-rich part is metallized to form a plurality of voids in the nitride embedding layer
Data Source
AI summary
A method of fabricating a gallium nitride (GaN) substrate provides a GaN thick film without causing bending and cracks which may occur in a growing process. To this end, a nitride embedding layer having a plurality of voids therein is embedded between a GaN layer and a base substrate. The method includes preparing a base substrate, growing, on the base substrate, the nitride embedding layer having a plurality of indium-rich parts at a first temperature, and growing a GaN layer on the nitride embedding layer at a second temperature higher than the first temperature so as to metallize the indium-rich part to form a plurality of voids in the nitride embedding layer.