SiC Buffer Layer Doping to Block Threading Dislocations
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Solution Overview
Problem
Silicon carbide substrates often have dislocation defects that can spread into epitaxially grown layers, leading to defects in the resulting silicon carbide epitaxial layer during epitaxial growth.
Innovation Solution
A buffer layer is formed on the silicon carbide substrate by creating multiple layers of silicon carbide films, where the top surface of each layer is doped with predetermined ions to a thickness less than 10 nm, acting as a barrier to block the upward propagation of threading dislocation defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon carbide epitaxial layer is grown directly on a silicon carbide substrate, then the epitaxial layer has higher quality and better electrical properties, but dislocation defects from the substrate spread into the epitaxial layer causing defects
Solution Approach 1:
The buffer layer is segmented into multiple alternating layers of undoped silicon carbide and doped silicon carbide regions. This segmentation creates multiple barriers within the buffer layer that collectively block dislocation propagation while maintaining overall structural integrity and electrical performance.
Solution Approach 2:
The buffer layer acts as an intermediary structure between the substrate and the epitaxial layer. It provides a transition zone that filters out dislocation defects while allowing the high-quality epitaxial growth to proceed, thus mediating between the defective substrate and the quality-requiring epitaxial layer.
2Reliability
If the top doped region thickness is increased to better block dislocations, then dislocation blocking improves, but the thickness of the silicon carbide film remaining under the doped region decreases
Solution Approach 1:
The doping concentration in the top doped region is increased to enhance dislocation blocking capability. By changing the doping parameter rather than increasing thickness, the buffer maintains adequate film thickness while achieving improved defect suppression through higher dopant concentration in the barrier regions.
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 buffer layer effectively diverts vertical propagation paths of threading dislocations into horizontal paths, preventing further upward spread and improving the quality of the silicon carbide epitaxial layer by confining dislocation defects within the top doped region.
Implementation Method 1
treating the surface of the silicon carbide film with predetermined ions so that a top doped region of the silicon carbide film around the top surface is doped with the predetermined ions
Implementation Method 2
The buffer layer effectively diverts vertical propagation paths of threading dislocations into horizontal paths, preventing further upward spread and improving the quality of the silicon carbide epitaxial layer by confining dislocation defects within the top doped region
Data Source
Figure 1~3
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AI summary
A buffer layer on a silicon carbide substrate and a method of forming the same are disclosed. The buffer layer includes at least two layers of silicon carbide films, in which at least each lower one is doped at a top surface thereof with predetermined ions. As a result, at the top surface of the silicon carbide film, a barrier with different parameter is formed, which can block dislocation defects that have spread into the silicon carbide film from further upward propagation in the silicon carbide film.