GaN Substrate Beveling Angle for Temperature Uniformity
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Solution Overview
Problem
Conventional group III nitride semiconductor substrates with beveling angles of 5° to 30° suffer from edge crown formation, chipping, and susceptor damage during epitaxial growth, leading to uneven temperature distribution and handling issues.
Innovation Solution
A group III nitride semiconductor substrate with beveled portions on both the group III and nitric polarity faces, featuring a beveling angle of over 30° to 60° on the nitric polarity face to enhance temperature uniformity and handleability, and a smooth transition between the arc and orientation flat portions to prevent susceptor damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the beveling angle is set to 5° to 30° to facilitate substrate handling, then the substrate can be easily picked up with tweezers, but edge crown formation occurs during epitaxial growth and temperature distribution becomes uneven
Solution Approach 1:
The patent changes the beveling angle parameter from the conventional 5° to 30° range to a steeper 60° to 80° range. This parameter change simultaneously improves temperature distribution uniformity during epitaxial growth (reducing edge crown) while maintaining ease of substrate handling through the modified geometric configuration
Solution Approach 2:
The patent applies different beveling angles to different regions of the substrate periphery. The main arc portions have beveling angles of 60° to 80° for optimal temperature distribution, while the transition regions to the orientation flat have different configurations. This local differentiation resolves the contradiction by optimizing each region for its specific function
2Ease of operation
If the beveling width is increased to ease substrate handling, then the substrate can be easily gripped, but the contact area with the susceptor decreases causing uneven temperature distribution
Solution Approach 1:
The patent changes the beveling angle parameter to 60° to 80°, which allows for a narrower beveling width to achieve the same handling ease. This narrower width maintains sufficient contact area with the susceptor for uniform temperature distribution while still providing adequate grip surface for tweezers
Solution Approach 2:
The patent differentiates the beveling configuration between the arc portions (with 60° to 80° angles for temperature uniformity) and the transition regions to orientation flat (with different configurations for handling). This local differentiation allows each region to optimize its function without compromising the other
3Measurement precision
If the substrate has angular portions at the transition between arc part and orientation flat, then the substrate can be precisely oriented, but the angular portions contact and damage the silicon carbide coating on the susceptor
Solution Approach 1:
The patent replaces the conventional sharp angular transitions between the arc part and orientation flat with smooth curved transitions. This curvature elimination prevents stress concentration and contact damage to the susceptor coating while maintaining precise orientation capability through the preserved flat reference surfaces
Solution Approach 2:
The patent proactively designs the substrate geometry to prevent the harmful effect of susceptor damage before it occurs. By eliminating angular portions that would contact the susceptor, the design preemptively prevents coating damage and particle generation, addressing the problem before it manifests during processing
Data Source
AI summary
A GaN substrate 1, a group III nitride semiconductor substrate, is provided with an OF portion 2 for the periphery thereof. The bevel 7 on the periphery of the nitric polarity face 5 side of the GaN substrate 1 is provided throughout the entire periphery of the GaN substrate 1 including the OF portion 2, wherein the beveling angle θ2 of the bevel 7 is given a value in the range over 30° to 60° inclusive.