SiC Crystal Facet Removal for Uniform Doping
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Solution Overview
Problem
The existing silicon carbide (SiC) crystal growth methods, particularly the physical vapor transportation (PVT) method, result in facet regions with higher doping concentrations and electrical resistivity, leading to inconsistent electrical properties and defects in SiC devices, which affect yield, performance, and reliability.
Innovation Solution
A SiC crystal with a facet only at the edge is grown using the PVT method, where the facet region is directly fixed to the edge during growth and subsequently removed, resulting in a facet-free crystal bar, wafer, and substrate with improved uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the PVT method is used to grow SiC crystal, then the crystal can be formed with facet regions, but the doping concentration and electrical resistivity become inconsistent across different regions
Solution Approach 1:
The patent extracts and removes the facet region from the SiC crystal structure. By controlling the crystal growth to form a facet region that can be subsequently removed through machining, the harmful facet structure is eliminated, leaving only the uniform non-facet region in the final product, thus resolving the electrical property inconsistency
Solution Approach 2:
The patent segments the crystal structure by clearly defining and separating the facet region from the non-facet region. This segmentation allows for selective removal of the facet region while preserving the uniform non-facet region, achieving consistent electrical properties across the usable crystal area
2Ease of manufacture
If the facet region is present in the SiC crystal, then the crystal structure is complete, but the device yield and reliability decrease due to defects
Solution Approach 1:
The patent removes the facet region which contains defects and harmful properties. By extracting this problematic region through controlled machining after growth, the remaining crystal structure maintains completeness and structural integrity while eliminating the reliability-threatening defects
Solution Approach 2:
The patent takes preliminary action during the crystal growth process to form a facet region that can be easily identified and removed. This preliminary formation of the facet region with distinct characteristics enables subsequent selective removal, preventing defects from affecting the final device reliability
3Device complexity
If conventional PVT method is used, then the crystal growth process is simple, but the cost increases due to material loss from quality problems
Solution Approach 1:
The patent extracts only the necessary facet region for removal, minimizing material loss. By precisely controlling the location and size of the facet region and removing only this specific area through machining, the majority of the crystal material is preserved and can be used for device fabrication, thus reducing overall material yield loss
Solution Approach 2:
The patent applies local quality control by creating a specific facet region with distinct properties at a localized area of the crystal. This localized structural characteristic allows for targeted removal of only the problematic region while preserving the high-quality non-facet regions, maximizing usable material
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 approach reduces defects, improves doping and carrier concentration uniformity, and enhances the electrical properties of SiC substrates, leading to higher yield, performance, and reliability of SiC devices, while also reducing production costs.
Implementation Method 1
a SiC crystal with a facet only at an edge is grown using the PVT method
Implementation Method 2
A facet is an inherent attribute existing when a SiC crystal is prepared by a sublimation method
Data Source
AI summary
A high-uniformity SiC crystal, a crystal bar, a substrate and a semiconductor device are provided. The SiC crystal is obtained by direct growth through a PVT method without subsequent machining, and includes a facet region and a non-facet region. The facet region is located on an outer-circumference end face of the SiC crystal. A doping concentration change rate of the facet region is 1.5 times or above that of the non-facet region; and/or a carrier concentration change rate of the facet region is 5 times or above that of the non-facet region.