Alumina Substrate with Rare Earth Buffer for AlN Crystal Growth
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Solution Overview
Problem
The challenge is to reduce warping and defects in alumina substrates when growing aluminum nitride (AlN) crystals, particularly due to lattice mismatching and thermal expansion coefficient differences, which affects the quality and yield of semiconductor thin-film layers in devices like light emitting diodes and power transistors.
Innovation Solution
An alumina substrate with a formed AlN layer and rare earth elements-containing layers or regions at the interface or within the AlN layer is used to concentrate internal stress, thereby reducing warping and facilitating spontaneous peeling of the AlN crystal during growth, allowing for higher quality AlN crystal production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If AlN single crystal is grown on sapphire or SiC substrate to obtain independent AlN substrate, then lattice matching is improved, but internal stress accumulation causes defects, cracks and warping
Solution Approach 1:
A buffer layer is introduced between the AlN crystal and the sapphire/SiC substrate to act as an intermediary that accommodates lattice mismatch and reduces stress accumulation, preventing defects and cracks while maintaining good lattice matching
Solution Approach 2:
The thickness of the AlN layer is controlled within a specific range (10-100 μm) to optimize the balance between achieving sufficient lattice matching and minimizing stress accumulation, with the buffer layer parameters also optimized to reduce internal stress
2Manufacturing precision
If AlN layer thickness is increased to reduce substrate influence, then independent AlN substrate quality is improved, but growth time and cost increase
Solution Approach 1:
The buffer layer serves as a mediator that enables high-quality AlN crystal growth at reduced thickness (10-100 μm) by providing a stress-relief interface, eliminating the need for thick AlN layers and associated long growth times
Solution Approach 2:
Optimizing the AlN layer thickness parameter to 10-100 μm with the buffer layer structure achieves the desired substrate independence and crystal quality without requiring excessive thickness, thereby reducing growth time and cost
3Manufacturing precision
If multiple AlN layers are grown on independent AlN substrate to improve quality, then crystal quality is improved, but process complexity and cost increase
Solution Approach 1:
The buffer layer acts as a single intermediary structure that enables high-quality AlN crystal growth without requiring multiple AlN layers, simplifying the growth process while maintaining or improving crystal quality
4Ease of manufacture
If sapphire or SiC substrate is used as base, then substrate availability and cost are improved, but lattice mismatch causes internal stress and defects
Solution Approach 1:
The buffer layer serves as an intermediary between the sapphire/SiC substrate and the AlN crystal, enabling the use of readily available and cost-effective sapphire or SiC substrates while compensating for lattice mismatch and preventing defect formation
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
This approach effectively decreases warping and defects in the AlN layer, enabling the production of high-quality AlN crystals with reduced stress, improving the semiconductor layer's quality and ease of substrate separation, thus enhancing the manufacturing efficiency and cost-effectiveness of devices.
Implementation Method 1
a rare earth elements-containing layer and/or rare earth elements-containing regions is/are formed in the interior of the AlN layer or the interface between the AlN layer and the alumina substrate. Internal stress and deformation caused by lattice mismatching will be concentrated in a rare earth elements-containing layer and/or rare earth elements-containing regions
Data Source
AI summary
An alumina substrate wherein an AlN layer is formed on a surface of the alumina substrate and a rare earth elements-containing layer and/or rare earth elements-containing regions is/are formed in the interior of the AlN layer or in the interface between the AlN layer and the alumina substrate.