GaN Crystal Growth Oxygen Control
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Solution Overview
Problem
The existing flux method for producing Group III nitride semiconductors faces issues with anomalous growth at the periphery of the seed substrate, warpage, and the generation of miscellaneous crystals, which affect the crystallinity and yield of the semiconductor crystals due to oxygen incorporation and impurities.
Innovation Solution
Controlling the oxygen concentration in the furnace atmosphere during growth and modifying the surface modification weight ratio of the sodium flux to suppress anomalous growth and warpage, while also circulating and purifying the sodium to reduce impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the flux method is used to grow Group III nitride semiconductor crystals, then crystal growth can be achieved, but oxygen is readily incorporated into the crystal causing lattice distortion and warpage
Solution Approach 1:
The patent applies inert atmosphere by introducing a nitrogen-containing gas into the furnace to create an oxygen-free environment during crystal growth. This prevents oxidation of the sodium flux and subsequent oxygen incorporation into the GaN crystal, thereby maintaining crystal uniformity while enabling continuous growth operation.
Solution Approach 2:
The patent modifies the chemical composition parameters of the furnace atmosphere by controlling oxygen concentration and introducing nitrogen-containing gases. This parameter change prevents harmful oxygen incorporation while maintaining conditions suitable for GaN crystal growth from the sodium flux.
2Ease of manufacture
If sodium is used as flux and heated in contact with air, then melting and crystal growth can occur, but the surface of Na liquid oxidizes requiring complex purification apparatus
Solution Approach 1:
The patent eliminates the need for complex purification apparatus by conducting the entire crystal growth process in a nitrogen-containing atmosphere. This inert environment prevents sodium surface oxidation from the beginning, making gloveboxes and purification apparatus unnecessary while maintaining ease of manufacture.
Solution Approach 2:
The patent extracts oxygen from the furnace atmosphere by introducing nitrogen-containing gas, thereby removing the harmful oxidizing environment that would require complex purification systems. This simplifies the overall apparatus while maintaining sodium purity during crystal growth.
3Productivity
If oxygen concentration in furnace atmosphere is not controlled, then growth can proceed, but anomalous growth occurs at the periphery of the seed substrate
Solution Approach 1:
The patent introduces a nitrogen-containing gas to create an inert atmosphere that uniformly prevents oxidation throughout the furnace, including at the periphery of the seed substrate. This eliminates the oxygen concentration gradients that cause anomalous growth while maintaining overall growth productivity.
Solution Approach 2:
The patent ensures uniform inert atmosphere distribution throughout the furnace, providing consistent oxygen exclusion at all locations including the periphery of the seed substrate. This local quality control prevents anomalous growth while maintaining uniform crystal development across the entire substrate surface.
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 suppresses anomalous growth and warpage, improves the uniformity and quality of the semiconductor crystals, and enhances the reproducibility and yield of the production process.
Implementation Method 1
nitrogen is dissolved in a molten mixture of an alkali metal and a Group III element
Implementation Method 2
the oxygen concentration of the atmosphere inside the furnace is elevated after the growth initiation temperature
Data Source
AI summary
The present invention suppresses anomalous growth of a Group III nitride semiconductor at the periphery of a seed substrate. The invention is directed to a method for producing a Group III nitride semiconductor including feeding a nitrogen-containing gas into a molten mixture of a Group III metal and a flux placed in a furnace, to thereby grow a Group III nitride semiconductor on a seed substrate. The oxygen concentration of the furnace internal atmosphere is elevated after the growth initiation temperature of the Group III nitride semiconductor has been achieved. In a period from the initiation of the growth to a certain timing, the oxygen concentration of the furnace internal atmosphere is controlled to 0.02 ppm or less, and thereafter, to greater than 0.02 ppm and 0.1 ppm or less.