SiC BJT Defect Termination Layer for Dislocation Control
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Solution Overview
Problem
Silicon carbide (SiC) bipolar junction transistors (BJTs) are prone to degradation due to the growth of stacking faults induced by minority carrier injection, which affects their performance and stability, especially in high-power and high-temperature applications, and existing manufacturing methods fail to effectively reduce basal plane dislocation density without compromising device morphology.
Innovation Solution
A method of manufacturing SiC BJTs that involves forming a defect termination layer (DTL) between the substrate and the collector region, with specific thickness and doping levels to terminate basal plane dislocations and prevent the growth of stacking faults, thereby enhancing device stability and reducing the number of defects in the active regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard commercial-grade epitaxy is used to manufacture SiC BJTs, then the manufacturing process is simple and cost-effective, but the basal plane dislocation density remains high (100-200 cm^-2), resulting in device degradation
Solution Approach 1:
The patent applies preliminary action by growing a defect termination layer (DTL) before forming the active device regions. This DTL is specifically designed to terminate basal plane dislocations (BPDs) at its interface with the substrate, preventing them from propagating into the collector and base regions. The DTL serves as a pre-established barrier that stops defect propagation before the main device structure is completed, thereby achieving low dislocation density in active regions without requiring complete elimination of BPDs from the substrate.
Solution Approach 2:
The defect termination layer acts as an intermediary between the substrate and the active device regions. It mediates the interaction between BPDs originating from the substrate and the sensitive active regions by providing a transition zone where dislocations are terminated or pinned. This intermediary layer allows the device to be manufactured on substrates with moderate dislocation densities while achieving high reliability in the active regions.
2Reliability
If the thickness and doping level of the defect termination layer are increased to better terminate dislocations, then device reliability improves, but the manufacturing complexity and process time increase
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness and doping level of the defect termination layer to achieve the desired balance between reliability and manufacturing simplicity. Specific parameter ranges are identified: thickness of 5-20 micrometers and doping levels of 10^16-10^18 atoms/cm³. These parameter optimizations allow the DTL to effectively terminate BPDs while maintaining reasonable manufacturing complexity and process times.
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 results in stable SiC BJTs with reduced bipolar degradation, allowing for the production of high-power devices with improved reliability and extended operational stability, even in large-area devices, without deteriorating the device morphology, thus addressing the limitations of prior art methods.
Implementation Method 1
adjusting the thickness and the doping level of the DTL to terminate BPDs in the DTL and to prevent the growth of SFs from the DTL to the collector layer
Data Source
AI summary
A method of manufacturing a silicon carbide (SiC) bipolar junction transistor (BJT) and a SiC BJT are provided. The SiC BJT comprises an emitter region, a base region and a collector region. The collector region is arranged on a substrate having an off-axis orientation of about 4 degrees or lower. Further, a defect termination layer (DTL) is arranged between the substrate and the collector region. A thickness and a doping level of the DTL are configured to terminate basal plane dislocations in the DTL and reduce the growth of defects from the DTL to the collector region. At least some of the embodiments are advantageous in that SiC BJTs with improved stability are provided. Further, a method of evaluating the degradation performance of a SiC BJT is provided.