SiC Single Crystal Wafer Screw Dislocation Reduction
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Solution Overview
Problem
The challenge is to reduce screw dislocation density in silicon carbide (SiC) single crystal substrates grown by the Physical Vapor Transport (PVT) method, as high screw dislocation densities degrade the performance of SiC devices and existing methods either have insufficient effect or are not industrially viable due to low growth rates.
Innovation Solution
A method involving specific growth conditions where a silicon carbide single crystal is grown with a structural conversion layer to convert screw dislocations into stacking faults, resulting in a substrate with significantly reduced screw dislocation density, particularly in the peripheral region, by adjusting growth atmosphere pressure and temperature, allowing for higher growth rates and industrial scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional PVT method is used for SiC single crystal growth, then high growth rate and industrial scalability are achieved, but high screw dislocation density degrades device performance
Solution Approach 1:
A structural conversion layer is formed at the initial stage of crystal growth to convert screw dislocations into stacking faults before they propagate into the bulk crystal. This preliminary action prevents dislocation multiplication during subsequent high-rate growth, enabling both high productivity and device performance.
Solution Approach 2:
The invention converts harmful screw dislocations into less harmful stacking faults through controlled structural conversion during growth. By transforming the nature of the defect rather than simply removing it, the method maintains high growth rates while reducing the impact on device performance.
2Reliability
If MSE method or CVD method is used to reduce screw dislocations, then low screw dislocation density is achieved, but growth rate becomes 1/10 or less of PVT method making it difficult for industrial production
Solution Approach 1:
The structural conversion layer is applied locally at the seed crystal interface rather than throughout the entire growth process. This localized treatment reduces dislocations only where they originate, allowing the bulk of the crystal to grow at high speed using the PVT method, thus maintaining both low dislocation density and high productivity.
Solution Approach 2:
The conversion layer is formed preliminarily during the initial growth stage, converting dislocations before they can propagate. This early intervention allows subsequent growth to proceed rapidly without generating new dislocations, combining the defect-reduction benefit of slow methods with the speed of PVT growth.
3Reliability
If existing PVT method variations are used to reduce screw dislocations, then some reduction is achieved, but screw dislocation density remains at 10³ to 10⁴ (/cm²) which is insufficient for high performance devices
Solution Approach 1:
The invention introduces specific parameter changes in the structural conversion layer, including controlling the thickness to 1-10 μm and adjusting the composition ratio of SiC to SiO₂ (where SiO₂ content is 1-50 at%). These precise parameter controls enable effective dislocation conversion while maintaining crystal quality suitable for high-performance devices.
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 results in a SiC single crystal substrate with substantially lower screw dislocation density, enhancing device performance and yield, and enabling the production of high-quality substrates suitable for high-performance electronic devices.
Implementation Method 1
a SiC sublimation raw material is contained in a crucible, then, a seed crystal composed of a SiC single crystal is attached to the lid of the crucible, and the raw material is sublimated, whereby recrystallization causes the SiC single crystal to grow on the seed crystal
Implementation Method 2
the raw material is sublimated, whereby recrystallization causes the SiC single crystal to grow on the seed crystal
Data Source
AI summary
Provided are a method for manufacturing a SiC single crystal having high crystal quality and, in particular, extremely low screw dislocation density and a SiC single crystal ingot obtained by the method. In particular, provided is a silicon carbide single crystal substrate that is a substrate cut from a bulk silicon carbide single crystal grown by the Physical Vapior Transport (PVT) method, in which the screw dislocation density is smaller in the peripheral region than in the center region, so that screw dislocations are partially reduced.The method is a method for manufacturing a SiC single crystal by the PVT method using a seed crystal and the ingot is a SiC single crystal ingot obtained by the method. Particularly, the silicon carbide single crystal substrate is a silicon carbide single crystal substrate in which when, by representing the diameter of the substrate as R, a center circle region having a diameter of 0.5×R centered around a center point O of the substrate and a doughnut-shaped peripheral region remaining by excluding the center circle region are defined, the average value of screw dislocation densities observed in the doughnut-shaped peripheral region is 80% or less of the average value of screw dislocation densities observed in the center circle region.