SiC Epitaxial Structure Carbon Vacancy Reduction for Carrier Lifetime
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Solution Overview
Problem
High voltage, high current SiC semiconductor devices face limitations due to low carrier lifetime in N-type and P-type epitaxial layers, leading to high ON state resistance and conduction power loss, which is difficult to improve without increasing defect densities in epitaxial layers.
Innovation Solution
A semiconductor die with a silicon carbide epitaxial structure that includes N-type and P-type layers and carbon vacancy reduction material, implanted and annealed to diffuse carbon atoms throughout the structure, increasing carrier lifetime and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If epitaxial growth techniques are used to increase carrier lifetimes (lower temperature growth or lower silicon-to-carbon ratio), then carrier lifetime is improved, but defect density increases making high voltage high current devices impractical
Solution Approach 1:
Carbon vacancy reduction material is implanted into the SiC epitaxial structure before final device fabrication. This preliminary action reduces carbon vacancies and extends carrier lifetime without requiring suboptimal epitaxial growth conditions, thereby avoiding increased defect density while achieving the desired carrier lifetime extension for high voltage, high current device operation
Solution Approach 2:
A carbon vacancy reduction material (such as Group III, V, or VIII elements, or hydrogen) is introduced as an intermediary substance. This material is implanted into the SiC epitaxial structure and, upon annealing, reduces carbon vacancies through diffusion and chemical interaction, thereby extending carrier lifetime without compromising material quality or increasing defect density
2Loss of energy
If carrier lifetime is increased in N-type and P-type epitaxial layers, then conduction power loss is reduced, but device complexity increases due to additional processing steps
Solution Approach 1:
The carbon vacancy reduction material implantation and annealing process is combined with existing device fabrication steps. The implantation can be performed using standard ion implantation equipment, and the annealing is integrated into the thermal processing steps already required for device formation, thereby reducing conduction power loss through extended carrier lifetime without significantly increasing overall device complexity
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 solution significantly increases the average carrier lifetime in SiC epitaxial structures, reducing carbon vacancies and enhancing the performance of high voltage, high current SiC semiconductor devices by at least three times, thereby minimizing power loss and improving device efficiency.
Implementation Method 1
carbon vacancy reduction material, which has been implanted into a surface of the SiC epitaxial structure
Implementation Method 2
annealed to mobilize the carbon vacancy reduction material to diffuse carbon atoms substantially throughout the SiC epitaxial structure
Implementation Method 3
the SiC epitaxial structure has been annealed to mobilize the carbon vacancy reduction material to diffuse carbon atoms substantially throughout the SiC epitaxial structure
Implementation Method 4
diffuse carbon atoms substantially throughout the SiC epitaxial structure, thereby increasing an average carrier lifetime
Data Source
AI summary
A semiconductor die and a process for fabricating the semiconductor die are disclosed. The semiconductor die has a substrate and a silicon carbide (SiC) epitaxial structure on the substrate. The SiC epitaxial structure includes at least a first N-type SiC layer, at least a first P-type SiC layer, and carbon vacancy reduction material, which has been implanted into a surface of the SiC epitaxial structure. Further, the SiC epitaxial structure has been annealed to mobilize the carbon vacancy reduction material to diffuse carbon atoms substantially throughout the SiC epitaxial structure, thereby increasing an average carrier lifetime in the SiC epitaxial structure.