SiC Epitaxial Wafer Defect Control via Dislocation Screening
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Solution Overview
Problem
The surface density of stacking faults and carrot defects in SiC epitaxial films is difficult to predict due to the propagation of basal plane dislocations and threading screw dislocations from the substrate, leading to increased on-resistance and reduced current flow areas in SiC devices.
Innovation Solution
A method to manufacture SiC epitaxial wafers by determining the upper limit of basal plane dislocation and threading screw dislocation densities on the substrate surface, using X-ray topography and photoluminescence to measure and reduce these defects, thereby forming epitaxial films with reduced stacking faults and carrot defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If basal plane dislocations are present on the substrate surface, then epitaxial films can be formed, but stacking faults and carrot defects propagate to the epitaxial film increasing on-resistance and reducing current flow areas
Solution Approach 1:
The patent applies preliminary action by measuring the surface density of basal plane dislocations and threading screw dislocations on the substrate before epitaxial film formation, and establishing upper limit values for these densities. By pre-screening substrates based on dislocation density measurements using X-ray topography and photoluminescence, the method prevents propagation of excessive defects to the epitaxial film, thereby reducing stacking faults and carrot defects while maintaining device performance
Solution Approach 2:
The patent implements feedback by using measurement results (X-ray topography and photoluminescence) to determine whether the substrate meets the upper limit criteria for dislocation densities. This feedback mechanism allows selective use of substrates that will produce epitaxial films with acceptable defect levels, creating a closed-loop quality control system that correlates substrate dislocation density with epitaxial film quality
2Manufacturing precision
If substrate dislocation density is reduced to minimize defects, then epitaxial film quality improves, but substrate selection and measurement complexity increases
Solution Approach 1:
The patent applies universality by using two different measurement techniques (X-ray topography and photoluminescence) that serve multiple functions: they both detect basal plane dislocations and threading screw dislocations, and they provide complementary information about substrate quality. This multi-functional approach allows comprehensive substrate characterization through established methods, improving epitaxial film quality while managing measurement complexity through technique integration
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 method effectively reduces the surface density of stacking faults and carrot defects in SiC epitaxial films, improving the quality and performance of SiC devices by enhancing current flow and reducing on-resistance.
Implementation Method 1
Known examples of methods used to non-destructively detect crystal defects such as dislocations or stacking faults contained in SiC single crystal substrates and SiC epitaxial wafers, where an epitaxial film is formed on the substrate, include X-ray topography
Implementation Method 2
Known examples of methods used to non-destructively detect crystal defects such as dislocations or stacking faults contained in SiC single crystal substrates and SiC epitaxial wafers, where an epitaxial film is formed on the substrate, include photoluminescence
Implementation Method 3
These SiC devices are normally fabricated using SiC epitaxial wafers obtained by growing a SiC epitaxial film serving as the active region of the device by a method such as chemical vapor deposition (CVD) on a SiC single crystal substrate
Data Source
AI summary
A method of manufacturing a SiC epitaxial wafer wherein a SiC epitaxial layer is provided on a SiC single crystal substrate having an off angle. The method includes determining a ratio of basal plane dislocations (BPD) which cause stacking faults in a SiC epitaxial film of a prescribed thickness, to basal plane dislocations which are present on a growth surface of the SiC single crystal substrate, determining an upper limit of surface density of basal plane dislocations, preparing a SiC single crystal substrate which has surface density equal to or less than the above upper limit, and forming a SiC epitaxial film on the SiC single crystal substrate under the same conditions as the growth conditions of the epitaxial film used in the step of determining the ratio.