AlN Crystal Diameter Expansion via Thermal Gradient Control
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Solution Overview
Problem
The commercial feasibility of AlN-based semiconductor devices is limited by the scarcity and high cost of low-defect single crystals of AlN, and conventional diameter-expansion techniques for growing larger AlN crystals often result in defective material with basal plane dislocations.
Innovation Solution
The techniques involve establishing baseline radial thermal gradients using external thermal shielding and enhancing these gradients with internal thermal shields and atomic nitrogen plasma to achieve high rates of diameter expansion while maintaining high crystalline quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional diameter-expansion techniques are used to grow larger AlN crystals, then the crystal diameter increases, but the crystal quality deteriorates with basal plane dislocations
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting thermal field parameters during the crystal growth process. Specifically, it modifies radial and axial temperature gradients, introduces oscillating thermal fields, and adjusts heating power in zones to enable diameter expansion while suppressing basal plane dislocation formation. This allows the crystal diameter to increase without sacrificing quality.
Solution Approach 2:
The patent implements periodic action through oscillating thermal fields applied during crystal growth. By periodically varying the thermal conditions in the growth chamber, the process suppresses dislocation formation while enabling diameter expansion. The oscillating thermal field creates dynamic conditions that prevent stable dislocation nucleation and propagation.
2Productivity
If high growth rates are achieved through aggressive thermal field modification, then productivity increases, but defect density increases
Solution Approach 1:
The patent applies dynamics by using time-dependent thermal field modifications during crystal growth. The thermal parameters are dynamically adjusted in response to growth conditions, allowing high growth rates to be maintained while suppressing defect formation. The dynamic thermal field adaptation enables the system to optimize between speed and quality in real-time.
Solution Approach 2:
The patent implements feedback mechanisms where growth conditions are continuously monitored and thermal field parameters are adjusted accordingly. This feedback control allows the system to maintain high growth rates while preventing defect accumulation, as the thermal field is modified in real-time based on observed growth behavior and defect formation tendencies.
3Area of stationary object
If large diameter substrates are produced, then substrate area increases, but dislocation density increases particularly at edges
Solution Approach 1:
The patent applies local quality by implementing zone-specific thermal field control during crystal growth. Different radial and axial zones are treated with different thermal conditions to suppress dislocation formation at critical locations such as the crystal edges and surface. This localized thermal management allows large diameter substrates to be produced while maintaining low dislocation density across the entire area.
Solution Approach 2:
The patent implements segmentation by dividing the growth chamber into multiple thermal zones with independent control. This allows different regions of the growing crystal to experience optimized thermal conditions tailored to their specific requirements, preventing dislocation formation at edges and surfaces while maintaining overall crystal quality and enabling large substrate production.
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
These techniques enable the growth of large, high-quality AlN single crystals with minimal basal plane dislocations, facilitating cost-effective production of substrates and devices with improved UV transparency and optical performance.
Implementation Method 1
Vapor including, consisting essentially of, or consisting of aluminum and nitrogen is condensed within the growth chamber, thereby forming on the growth face of the seed crystal an AlN single crystal
Implementation Method 2
A radial thermal gradient and an axial thermal gradient are established within the growth chamber
Implementation Method 3
The vapor may be enhanced with atomic nitrogen proximate an edge portion of the AlN single crystal
Data Source
AI summary
In various embodiments, aluminum nitride single crystals are rapidly diameter-expanded during growth and have large crystal augmentation parameters. The aluminum nitride single crystals advantageously have low densities of basal plane dislocations and large substrate versatility metrics.