SiC Crystal Growth DC Resistivity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in manufacturing high-quality silicon carbide (SiC) single crystals lies in the difficulty of accurately measuring and controlling the sublimation temperature of the starting material during the sublimation-recrystallization process, which affects the growth conditions and results in low productivity and quality due to the indirect measurement methods and high temperature variability.
Innovation Solution
The method involves using the DC equivalent resistivity calculated from the DC voltage and current values before converting them to high frequency, which correlates with the sublimation temperature, allowing for precise control of the growth conditions by adjusting the DC voltage or current to achieve a predetermined micropipe density, thereby improving the quality and yield of SiC single crystals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the sublimation-recrystallization method is used to grow SiC single crystals at ultra-high temperatures, then the quality and polytype control of the crystal is improved, but the difficulty of detecting and measuring the sublimation temperature increases, leading to low productivity
Solution Approach 1:
The patent introduces a refractory metal crucible as an intermediary medium between the heating source and the SiC starting material. The crucible's temperature, which can be measured by emission pyrometry, serves as a proxy for the sublimation temperature of the SiC material, enabling indirect but effective temperature control and measurement without direct contact with the ultra-high temperature SiC powder
Solution Approach 2:
The patent replaces direct mechanical or contact-based temperature measurement methods with optical measurement (emission pyrometry) to measure the crucible temperature. This non-contact optical measurement method enables accurate temperature detection at ultra-high temperatures without physical intrusion into the growth zone
2Manufacturing precision
If the sublimation temperature control is improved through better measurement, then the micropipe density and crystal quality are improved, but the device complexity increases due to additional measurement and control systems
Solution Approach 1:
The refractory metal crucible serves multiple functions: it contains the SiC starting material, withstands ultra-high temperatures, and acts as a temperature indicator through its emissivity characteristics. This multi-functionality reduces the need for separate temperature sensing devices directly in the growth zone, thereby limiting the increase in device complexity
Solution Approach 2:
The patent implements a feedback control system where the emission pyrometer continuously measures the crucible temperature, and this information is used to adjust the heating power to maintain the sublimation temperature within the optimal range. This automated feedback loop improves crystal quality while minimizing the need for complex manual intervention systems
3Manufacturing precision
If the growth conditions are tightly controlled to reduce micropipe density, then the crystal quality is improved, but the productivity decreases due to longer growth times and lower yield
Solution Approach 1:
The patent optimizes multiple growth parameters simultaneously: maintaining sublimation temperature within 2200-2600°C, controlling the temperature gradient between the crucible and seed crystal, and regulating the rotation speed. These coordinated parameter changes enable faster growth rates while maintaining low micropipe density, thereby improving productivity without sacrificing crystal quality
Solution Approach 2:
The patent employs a pre-formed seed crystal with the desired polytype structure (4H-SiC) before the main growth process. This preliminary preparation ensures that the crystal grows with the correct structure from the beginning, reducing defects and minimizing the need for post-growth processing or rejection, thus improving overall yield
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 enables more accurate detection of the thermal state of the starting material, leading to a higher success rate and improved quality of SiC single crystals by maintaining the sublimation temperature within a controlled range, enhancing the productivity and quality of crystal growth.
Implementation Method 1
surrounding a crucible holding a starting material powder and a seed crystal by an induction coil, supplying a high frequency current through the induction coil to heat the crucible
Implementation Method 2
making the starting material powder sublimate to grow a silicon carbide single crystal on the seed crystal
Implementation Method 3
The temperature of the seed crystal positioned at the center axis of the crucible can be estimated relatively precisely by the surface temperature of the crucible measured using an emission pyrometer
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
The present invention provides a method of manufacturing by the sublimation-recrystallization method more accurately detecting a thermal state of a starting material in a crucible and enabling control of the growth conditions while manufacturing an SiC single crystal. The method obtains the high frequency current to be supplied through the induction coil by a converter for converting AC current to DC current and an inverter means for converting the DC current output from the converter to a high frequency to obtain a high frequency current, obtains a grasp, in advance, of a relationship between a variation over time of a DC equivalent resistivity (DCV/DCI), calculated from a DC voltage value (DCV) and DC current value (DCI) converted by the converter at the time of growth of the silicon carbide single crystal, and a density of micropipes formed in the grown silicon carbide single crystal, and adjusts at least one of the DCV or DCI at the converter based on the relationship of the DC equivalent resistivity and micropipe density grasped in advance.