AlN Single Crystal Substrate Defect Density Control
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Solution Overview
Problem
AlN single crystal substrates used for deep ultraviolet light emitting elements often suffer from cracks during post-processing due to uneven dislocation density distribution, leading to reduced luminous efficiency and poor yield.
Innovation Solution
An AlN single crystal substrate with a three-layer structure is developed, where the defect density of the inside layer is higher than that of the front and back surfaces, effectively controlling the distribution of defects to suppress cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the dislocation density is reduced uniformly across the AlN single crystal substrate, then the defect density decreases, but cracks are more likely to occur during post-processing
Solution Approach 1:
The patent applies local quality by creating a non-uniform dislocation density distribution within the AlN single crystal substrate. Specifically, the substrate is designed to have a first region with lower dislocation density and a second region with higher dislocation density. This localized variation in defect density allows the substrate to maintain overall low defect levels while having specific regions that can accommodate stress and prevent crack propagation during post-processing operations.
2Ease of manufacture
If the AlN single crystal substrate is grown using conventional methods, then the production process is simple, but the dislocation density distribution is uneven leading to cracks
Solution Approach 1:
The patent applies preliminary action by controlling the dislocation density distribution during the crystal growth process itself. By adjusting growth parameters such as temperature gradient, pressure, and composition during the initial stages of AlN single crystal formation, the desired non-uniform dislocation density distribution is established before subsequent processing steps. This preliminary control of defect distribution prevents cracks during post-processing without requiring complex additional manufacturing steps.
Data Source
AI summary
Provided is an AlN single crystal substrate having a three-layer structure composed of one AlN single crystal as a whole and is classifiable into the first layer, the second layer, and the third layer in this order in the thickness direction in terms of defect density, wherein the second layer has a defect density of 10 times or more the defect density of each of the first layer and the third layer.