SiC Crystal Growth Dew Point Control
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Solution Overview
Problem
Existing methods for manufacturing silicon carbide single crystals fail to effectively control oxygen concentrations, leading to increased dislocations and stacking faults due to moisture impurities undetectable by conventional vacuum meters, which are critical for larger diameter substrates.
Innovation Solution
Incorporating a dew point instrument in the crystal growth apparatus to maintain a dew point of not more than −40° C, reducing oxygen inclusion and suppressing two-dimensional nucleus growth, thereby minimizing dislocations and stacking faults in silicon carbide single crystals and epitaxial substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional vacuum meters are used to monitor the growth atmosphere, then the device complexity is low, but the measurement precision of moisture impurities is insufficient leading to increased oxygen concentration in crystals
Solution Approach 1:
The patent replaces conventional vacuum meters with a dew point instrument that uses optical or electromagnetic measurement principles instead of mechanical vacuum gauging. This substitution enables precise detection of moisture levels (dew point temperature) in the growth atmosphere, directly addressing the measurement precision limitation while maintaining acceptable device complexity through standardized sensor technology.
2Manufacturing precision
If oxygen concentration is not controlled during crystal growth, then the manufacturing process is simple, but dislocations and stacking faults increase reducing crystal quality
Solution Approach 1:
The patent implements a feedback control system where the dew point instrument continuously monitors moisture content in the growth atmosphere, and this information feeds back to the gas supply and exhaust systems. By maintaining dew point at −40° C. or lower through active control, the system ensures oxygen concentration remains below 1×10^17 cm^−3, preventing dislocations and stacking faults while providing systematic process control.
Solution Approach 2:
The patent controls the physical parameter of dew point temperature in the growth atmosphere, maintaining it at −40° C. or lower throughout the crystal growth process. This parameter change directly influences oxygen solubility in the molten silicon, ensuring oxygen concentration stays below 1×10^17 cm^−3 and preventing crystal defects, thereby improving manufacturing precision through controlled atmospheric conditions.
3Productivity
If larger diameter substrates are manufactured, then the productivity increases, but the harmful effects of moisture impurities and oxygen inclusion are amplified
Solution Approach 1:
The patent applies preliminary anti-action by pre-controlling the growth atmosphere conditions before crystal growth begins. The dew point is maintained at −40° C. or lower and oxygen concentration is kept below 1×10^17 cm^−3 through controlled gas flow and exhaust systems before any significant crystal growth occurs. This preventive approach counteracts the amplified harmful effects of oxygen and moisture that would otherwise occur in larger diameter substrates, enabling high productivity without increased defect rates.
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 achieves silicon carbide substrates with oxygen concentrations of not more than 1×10^17 cm^−3, dislocation densities of not more than 2×10^4 cm^−2, and stacking fault area ratios of not more than 2.0%, significantly improving crystal quality and reducing defects.
Implementation Method 1
a dew point instrument disposed between the gas outlet and the exhaust pump, the dew point instrument being configured to measure a dew point of gas passing through the gas outlet
Implementation Method 2
a water-cooling portion configured to water-cool a portion at least including the welded portion
Implementation Method 3
an exhaust pump connected to the gas outlet
Implementation Method 4
growing a silicon carbide single crystal on the seed crystal by sublimating the source material
Data Source
AI summary
A crystal growth apparatus includes: a chamber including a gas inlet, a gas outlet, a welded portion, and a water-cooling portion configured to water-cool a portion at least including the welded portion; an exhaust pump connected to the gas outlet; a dew point instrument disposed between the gas outlet and the exhaust pump, the dew point instrument being configured to measure a dew point of gas passing through the gas outlet.