Group III Nitride Substrate Curvature Control for Lower Dislocation
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Solution Overview
Problem
Group III nitride single crystal substrates with improved radius of curvature and surface quality are needed to reduce variations in performance and increase the yield of light-emitting devices, as existing substrates suffer from lattice relaxation and dislocation issues due to variations in curvature and surface roughness.
Innovation Solution
A method involving X-ray rocking curve measurements and polishing techniques to achieve substrates with specific curvature radii and surface smoothness, ensuring a uniform crystal arrangement that suppresses lattice relaxation and dislocation density, thereby stabilizing the quality and yield of semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a group III nitride single crystal substrate is used to improve device performance, then emission performance is improved, but variance in radius of curvature causes variations in device composition and surface roughness
Solution Approach 1:
The invention changes the curvature radius parameter of the substrate from small (causing warpage) to large (reducing warpage), specifically achieving a curvature radius of 10 m or more. This parameter change directly addresses the variance in radius of curvature that causes device composition variations and surface roughness, while maintaining the emission performance benefits of group III nitride single crystal substrates
2Manufacturing precision
If polishing is performed to improve surface quality, then surface roughness is reduced, but time and process complexity increase
Solution Approach 1:
The invention performs preliminary actions during the crystal growth process itself to achieve better surface quality before polishing. By controlling the growth conditions and using appropriate seed substrates, the crystal grows with inherently better surface characteristics, reducing the amount of subsequent polishing needed and thereby reducing process time
3Productivity
If a sapphire substrate is used for mass production, then cost and productivity are improved, but lattice mismatch causes crystal defects and cracks
Solution Approach 1:
The invention uses group III nitride single crystal substrates that have homogeneous material composition and matched lattice constants with the epitaxial semiconductor layer. This homogeneity eliminates the lattice mismatch present in sapphire substrates, preventing misfit dislocations and cracks while maintaining mass production capability through optimized growth processes
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 method results in group III nitride single crystal substrates with improved curvature and surface quality, reducing variance in device performance and increasing the stability and yield of light-emitting and electronic devices by minimizing lattice relaxation and dislocation density.
Implementation Method 1
a 1/1000 intensity width of an X-ray rocking curve of a low-angle incident plane at a center of the first main face of the substrate is no more than 1200 arcsec
Implementation Method 2
polishing the surface of the first main face and the surface of the first back face
Data Source
AI summary
A group III nitride single crystal substrate comprises: a first main face; and a first back face opposite to the first main face, wherein an absolute value of a radius of curvature of the first main face of the substrate is 10 m or more; an absolute value of a radius of curvature of a crystal lattice plane at a center of the first main face of the substrate is 10 m or more; and a 1/1000 intensity width of an X-ray rocking curve of a low-incidence-angle face at the center of the first main face of the substrate is 1200 arcsec or less.