High Purity Carbonaceous Material Purification for Single Crystal Yield
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Solution Overview
Problem
Carbonaceous materials used in semiconductor and nuclear industries face challenges due to high impurity content, particularly oxygen, nitrogen, chlorine, phosphorus, sulfur, and boron, which affect the yield and quality of silicon carbide, gallium nitride, and calcium fluoride single crystals, leading to low production yields and crystal defects.
Innovation Solution
A high-purity carbonaceous material is developed through a purification process involving treatment in halogen-containing gases at high temperatures, followed by degassing and hydrogenation, reducing impurity concentrations to extremely low levels as analyzed by SIMS, thereby minimizing the incorporation of impurities in the crystal growth process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional graphite materials are used as furnace jigs, then manufacturing is simple and cost-effective, but impurity content (oxygen, nitrogen, chlorine, phosphorus, sulfur, boron) is high, causing low yield in single crystal production
Solution Approach 1:
The patent applies preliminary action by performing multiple purification treatments (halogen-containing gas treatment, vacuum degassing, hydrogen treatment) on the carbonaceous material before it is used as a furnace jig. This advance purification removes impurities such as oxygen, nitrogen, chlorine, phosphorus, sulfur, and boron, ensuring that when the material is subsequently used in single crystal growth, it does not contaminate the crystals, thereby achieving high yield without requiring complex in-process purification systems.
Solution Approach 2:
The patent applies parameter changes by transforming the carbonaceous material through controlled exposure to halogen-containing gases at elevated temperatures, followed by vacuum degassing to remove volatile impurities, and then hydrogen treatment to reduce oxygen content. These parameter changes (temperature, gas composition, pressure) systematically reduce impurity concentrations to levels below 1 ppm for most elements, resolving the contradiction between maintaining manufacturing feasibility and achieving the ultra-low impurity levels required for high-yield single crystal production.
2Reliability
If high purity graphite materials are used, then impurity content is reduced, but oxygen, nitrogen, chlorine, phosphorus, sulfur and boron bound to carbon atoms remain, causing crystal defects
Solution Approach 1:
The patent applies strong oxidants by using halogen-containing gases (such as chlorine or fluorine compounds) to treat the carbonaceous material at elevated temperatures. These halogen gases react with impurity elements bound to carbon atoms, forming volatile halides that can be removed. This accelerated chemical reaction effectively removes stubborn impurities like oxygen, nitrogen, phosphorus, sulfur, and boron that conventional purification methods cannot eliminate, achieving the ultra-high purity levels required for defect-free single crystal growth.
Solution Approach 2:
The patent uses hydrogen as an intermediary substance in the final treatment step. Hydrogen diffuses into the carbonaceous material and reacts with remaining oxygen and other impurities bound to carbon, forming volatile compounds that desorb during subsequent vacuum heating. This intermediary hydrogen treatment effectively removes the last traces of impurities that directly affect crystal quality, achieving oxygen content below 1×10^18 atoms/cm³ and eliminating crystal defects without requiring excessively complex direct purification methods.
3Reliability
If multiple purification treatments are applied, then impurity content is significantly reduced, but production cost and process complexity increase
Solution Approach 1:
The patent merges multiple purification functions into a integrated sequential process: halogen-containing gas treatment removes bulk impurities and those bound to carbon, vacuum degassing removes volatile impurities including those released from the material structure, and hydrogen treatment eliminates remaining oxygen and other impurities. By combining these treatments in a logical sequence where each step builds on the previous, the patent achieves comprehensive purification (reducing all major impurities to below 1 ppm levels) without requiring entirely separate complex systems, as the same furnace can potentially perform multiple treatments by changing gas atmosphere and pressure conditions.
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 high-purity carbonaceous material significantly reduces impurity concentrations, enhancing the quality of single crystals and preventing crystal defects, allowing for improved semiconductor and ceramic production with reduced impurity levels in both the materials and epitaxial growth layers.
Implementation Method 1
treatment in halogen-containing gases at high temperatures
Implementation Method 2
followed by degassing
Implementation Method 3
followed by degassing and hydrogenation
Implementation Method 4
having oxygen content of 1×1018 atoms/cm3 or less analyzed by SIMS (secondary ion mass spectrometry)
Data Source
AI summary
The invention provides a high purity carbonaceous material which is reduced in contents of oxygen, nitrogen and chlorine readily binding to carbon atoms and in contents of elements, phosphorus, sulfur and boron, readily binding to carbon atoms upon heating and which can be used in producing single crystals such as semiconductors, a high purity carbonaceous material for use as a substrate for ceramic layer coating, and a ceramic layer-coated high purity carbonaceous material. The high purity carbonaceous material has oxygen content of 1×1018 atoms/cm3 or less as determined by SIMS. Its chlorine content is preferably 1×1016 atoms/cm3 or less as determined by SIMS, and its nitrogen content is preferably 5×1018 atoms/cm3 or less as determined by SIMS. Its phosphorus, sulfur and boron contents are preferably not higher than respective specified values. Such a high purity carbonaceous material is coated with ceramic layer.