Gallium Nitride Substrate Stress Control via Notch Geometry
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gallium nitride wafers and group III nitride semiconductor substrates face high defect ratios due to cracking in flat and notch portions during manufacturing and epitaxial layer growth, with existing technologies failing to adequately address average dislocation density and residual stress in these regions.
Innovation Solution
A gallium nitride crystal substrate with a diameter of 50 mm to 155 mm and thickness of 300 μm to 800 μm, featuring flat and notch portions, contains oxygen, silicon, and carrier concentrations between 2×10^17 cm^-3 and 4×10^18 cm^-3, with average dislocation densities between 1000 cm^-2 and 5×10^7 cm^-2 and residual stresses between -10 MPa and 10 MPa in specific regions, thereby reducing crack defect ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flat portions and notch portions are formed on the substrate, then orientation identification and processing alignment are improved, but cracking defects increase due to stress concentration
Solution Approach 1:
The patent applies parameter changes by precisely controlling the curvature radius (R1, R2) of the flat and notch portions, the chamfering angles (α, β), and the depth of notch portions. These parameter optimizations balance the need for orientation identification with stress reduction, preventing cracking while maintaining measurement and alignment precision.
2Reliability
If dislocation density is reduced to improve crystal quality, then manufacturing complexity increases due to stricter process control requirements
Solution Approach 1:
The patent employs parameter changes in the crystal growth process, specifically controlling temperature gradients, pressure conditions, and composition ratios during HVPE growth. These parameter optimizations achieve low dislocation density (1×10^4 to 1×10^6 cm^-2) while maintaining feasible manufacturing processes.
3Reliability
If residual stress is controlled to prevent cracking, then manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes through precise control of chamfering angles (α: 30-60°, β: 10-30°) and curvature radii (R1: 0.5-5 mm, R2: 0.1-2 mm) at the flat and notch portions. These geometric parameter optimizations effectively manage residual stress distribution, preventing cracking while maintaining manufacturability.
4Productivity
If substrate diameter is increased to improve productivity, then defect density increases due to larger growth area
Solution Approach 1:
The patent applies local quality by implementing region-specific optimizations: the flat portions and notch portions have specially controlled curvature radii and chamfering angles to manage stress locally, while the central growth area maintains low dislocation density. This localized quality control enables large diameter substrates (150-200 mm) with uniformly low defect densities.
Data Source
AI summary
A gallium nitride crystal substrate has a diameter of 50-155 mm and a thickness of 300-800 μm and includes any of a flat portion and a notch portion in a part of an outer edge. The gallium nitride crystal substrate contains any of oxygen atoms, silicon atoms, and carriers at a concentration of 2×1017 to 4×1018 cm−3, and has an average dislocation density of 1000 to 5×107 cm−2 in any of a first flat region extending over a width from the flat portion to a position at a distance of 2 mm in a direction perpendicular to a straight line indicating the flat portion in a main surface and a first notch region extending over a width from the notch portion to a position at a distance of 2 mm in a direction perpendicular to a curve indicating the notch portion in the main surface.