Group 13 Nitride Base Substrate Stress Management
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Solution Overview
Problem
The existing technologies face challenges in reducing defects and cracks in group 13 nitride crystal layers during cooling from growth temperature to room temperature, leading to warping and film-formation failures in subsequent device formation.
Innovation Solution
A base substrate comprising an aluminum oxide supporting substrate with a base crystal layer of group 13 nitride, where a reaction product of aluminum and a group 13 element is formed between the substrate and the crystal layer, reducing stress and warping by generating a specific composition or metal of a group 13 element, thereby suppressing cracks and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a group 13 nitride crystal layer is grown on a sapphire substrate and then cooled from growth temperature to room temperature, then the crystal layer undergoes stress due to thermal expansion difference, but this results in warping and cracks in the crystal layer
Solution Approach 1:
A reaction product layer is introduced as an intermediary between the sapphire substrate and the group 13 nitride crystal layer. This reaction product, formed by reacting aluminum oxide from the substrate with group 13 elements during crystal growth, serves as a stress buffer that mediates the thermal expansion difference between substrate and crystal layer, preventing crack formation during cooling
Solution Approach 2:
The structure employs a composite material system consisting of sapphire substrate, reaction product layer, and group 13 nitride crystal layer. The reaction product layer has intermediate properties between the substrate and crystal layer, creating a gradient structure that reduces stress concentration and prevents cracking during thermal cycling
2Reliability
If irregularity is provided on the crystal growth surface of the base substrate, then dislocations and stress in the crystal are reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The reaction product layer is formed preliminarily during the crystal growth process itself, before subsequent device fabrication steps. This preliminary formation of the stress-buffering layer simplifies the overall process by combining stress management with the crystal growth step, avoiding additional complex surface treatment steps
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
The solution effectively reduces dislocation density and warping in group 13 nitride layers, enhancing the quality and reliability of subsequent functional devices by facilitating crystal growth and reducing defects.
Implementation Method 1
a stress is applied on the layer of the crystal of the group 13 nitride due to difference of thermal expansion of the supporting substrate and the layer of the crystal of the group 13 nitride
Implementation Method 2
a reaction product of a material of the supporting substrate and the crystal of the nitride of the group 13 element is present between the supporting substrate and the base crystal layer
Data Source
AI summary
A base substrate includes a supporting substrate comprising aluminum oxide, and a base crystal layer provided on a main face of the supporting substrate, comprising a crystal of a nitride of a group 13 element and having a crystal growth surface. At lease one of a metal of a group 13 element and a reaction product of a material of the supporting substrate and the crystal of the nitride of the group 13 element is present between the raised part and the supporting substrate. The reaction product contains at least aluminum and a group 13 element.