High-Temperature AlN Buffer Layer for Nitride Semiconductor Crystallinity
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Solution Overview
Problem
The existing methods for manufacturing nitride semiconductor crystals face challenges in achieving high crystallinity and favorable surface morphology due to the degradation of low-temperature buffer layers at elevated growth temperatures and the formation of hexagonal facets, which worsen the surface morphology and crystallinity of the GaN film.
Innovation Solution
A method involving the growth of a high-temperature AlN buffer layer at 900° C or higher, where the Al-source material is supplied continuously and the N-source material is supplied intermittently, resulting in a thin AlN buffer layer of 20 Å or smaller, which prevents Al incorporation into the nitride semiconductor crystal and maintains a favorable surface morphology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a low-temperature GaN buffer layer is formed at 500-800°C, then the crystallinity of the nitride semiconductor crystal is improved, but the buffer layer degrades when the growth temperature is raised to 1000°C or higher
Solution Approach 1:
The patent changes the temperature parameter from low-temperature (500-800°C) to high-temperature (900-1100°C) buffer layer formation, and adjusts the NH3/TMA mole ratio to 1800 or higher. This parameter change allows the buffer layer to maintain stability at high growth temperatures while still improving crystallinity, resolving the contradiction between crystallinity improvement and buffer layer stability.
2Manufacturing precision
If the film thickness of the buffer layer is reduced, then the crystal axis alignment is improved, but hexagonal facets form on the surface worsening the surface morphology
Solution Approach 1:
The patent changes the NH3/TMA mole ratio to 1800 or higher and forms the buffer layer at high temperature (900-1100°C). These parameter changes enable the formation of a thin buffer layer without hexagonal facet formation, allowing both good crystal axis alignment and favorable surface morphology to be achieved simultaneously.
3Stability of the object's composition
If a high-temperature AlN buffer layer is formed at 900°C or higher, then the thermal distortion is reduced, but the surface morphology deteriorates with hexagonal facet formation
Solution Approach 1:
The patent increases the NH3/TMA mole ratio to 1800 or higher while forming the buffer layer at high temperature (900-1100°C). This parameter change suppresses hexagonal facet formation during high-temperature buffer layer growth, allowing both thermal stability and favorable surface morphology to be achieved.
4Shape
If the NH3/TMA mole ratio is increased to maintain favorable surface flatness, then the surface morphology is improved, but Al incorporation into the crystal increases worsening the crystallinity
Solution Approach 1:
The patent sets the NH3/TMA mole ratio to 1800 or higher during buffer layer formation at high temperature (900-1100°C). This specific parameter combination allows high surface flatness to be achieved while preventing Al incorporation into the crystal, as the high temperature enables proper crystal growth despite the high NH3 concentration.
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 prevents the degradation of the AlN buffer layer, reduces thermal distortion, and achieves improved crystallinity and surface morphology of the nitride semiconductor crystal, with a high NH3/TMA mole ratio maintaining a favorable surface flatness and crystallinity.
Implementation Method 1
the AlN buffer layer is formed at a growth temperature of 900° C. or higher
Implementation Method 2
the crystal growth of a nitride semiconductor is preceded by the growth of an AlN buffer layer on top of a growth substrate
Data Source
AI summary
The present invention provides a method of manufacturing a nitride semiconductor capable of improving the crystallinity and the surface state of the nitride semiconductor crystal formed on top of a high-temperature AlN buffer layer. An AlN buffer layer is formed on top of a growth substrate, and then nitride semiconductor crystals are grown on top of the AlN buffer layer. In a stage of manufacturing the nitride semiconductor, the crystal of the AlN buffer layer is grown at a high temperature of 900° C. or higher. In addition, an Al-source material of the AlN buffer layer is started to be supplied first to a reaction chamber and continues to be supplied without interruption, and then a N-source material is supplied intermittently.