AlN Buffer Layer Annealing for Nitride Semiconductor Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for manufacturing nitride semiconductor substrates, particularly those using sapphire substrates, face challenges in achieving high-quality AlN layers with a flat surface due to lattice mismatch and crystal defects, leading to difficulties in obtaining substrates with low defect density and adequate crystallinity.
Innovation Solution
A method involving the formation of a precursor AlN buffer layer by sputtering, followed by annealing in an inert gas atmosphere at a temperature higher than the buffer layer formation temperature, while limiting substrate movement and maintaining a gas-tight state to prevent surface roughening and enhance crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If AIN layer is grown on sapphire substrate, then inexpensive substrate can be used, but lattice mismatch causes many threading dislocations and crystal defects
Solution Approach 1:
The patent introduces an AlN buffer layer as an intermediary between the sapphire substrate and the AIGaN light emitting layer. This buffer layer absorbs the lattice mismatch stress and prevents threading dislocations from propagating into the active layer, thereby maintaining high crystal quality while using inexpensive sapphire substrates
Solution Approach 2:
The patent employs low-pressure metalorganic chemical vapor deposition (MOCVD) to grow the AlN buffer layer under specific parameter conditions (low pressure, controlled temperature, specific gas flow rates). These parameter changes enable the formation of a high-quality buffer layer with reduced defect density, resolving the contradiction between substrate cost and crystal quality
2Ease of manufacture
If AIN layer is deposited on sapphire substrate, then substrate is available, but surface roughness increases and flat surface cannot be obtained
Solution Approach 1:
The patent performs preliminary growth of an AlN buffer layer on the sapphire substrate before depositing the AIGaN layer. This preliminary action creates a flat, defect-reduced surface that serves as a foundation for subsequent high-quality layer growth, preventing surface roughness issues
Solution Approach 2:
The AlN buffer layer acts as an intermediary that decouples the surface morphology issues of the sapphire substrate from the requirements of the AIGaN layer. It provides a flat, crystalline surface that eliminates the direct interface between sapphire and the light emitting layer
3Manufacturing precision
If high-temperature annealing is performed to improve crystallinity, then crystal quality improves, but surface components sublimate and form hollows
Solution Approach 1:
The patent performs the annealing process in an inert atmosphere (nitrogen or argon gas environment) to prevent oxidation and reduce sublimation of surface components. This inert environment allows high-temperature treatment to improve crystallinity without causing surface degradation and hollow 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 results in the production of nitride semiconductor substrates with a flat and high-quality AlN surface, significantly improving crystallinity and reducing surface roughness, thereby overcoming the limitations of previous techniques.
Implementation Method 1
annealing in an inert gas atmosphere at a temperature higher than the buffer layer formation temperature
Implementation Method 2
formation of a precursor AlN buffer layer by sputtering
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3A
AI summary
A method for manufacturing a nitride semiconductor substrate (1) includes: a preparation step (S10) of preparing a sapphire substrate (2); and a buffer layer forming step (S16) of forming an AIN buffer layer (3) on the sapphire substrate (2), wherein the buffer layer forming step (S16) includes: a group III nitride semiconductor forming step (S16a) of forming a precursor (3a) of an AIN buffer layer on the sapphire substrate (2); and an annealing step (S16b) of annealing the sapphire substrate (2) on which the precursor (3a) of the AIN buffer layer is formed in a gas-tight state in which a principal surface of the precursor (3a) of the AIN buffer layer is covered with a cover member (such as a sapphire substrate (102)) for inhibiting a component of the group III nitride semiconductor from dissociating from the principal surface of the formed precursor (3a) of the AIN buffer layer.