SiC FLR Structure for Edge Termination Reliability
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices face reliability issues due to precision variations in field limiting ring (FLR) structures and long edge termination regions, which increase costs and reduce reliability.
Innovation Solution
A semiconductor device with a FLR structure in the edge termination region, featuring FLRs with reduced impurity concentration and increased thickness, allowing for wider intervals and a shorter edge termination length, enhancing precision and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional FLR structures are used in silicon carbide semiconductor devices, then the edge termination region can provide voltage withstanding capability, but precision variations in FLR structures occur and reliability is reduced
Solution Approach 1:
The patent changes the physical parameters of the FLR structure by increasing the thickness of the p-type semiconductor layer from conventional thin layers to specifically 0.7-1.1 μm, and reducing impurity concentration to 1×10^18/cm³ or less. These parameter changes make the FLR structure less sensitive to manufacturing precision variations while maintaining voltage withstanding capability.
Solution Approach 2:
The patent applies different impurity concentrations to different regions: the FLR structure has low impurity concentration (1×10^18/cm³ or less) for precision and voltage withstanding, while the drift region has higher impurity concentration for current conduction. This local quality differentiation optimizes both reliability and manufacturing precision.
2Manufacturing precision
If conventional FLR structures with standard thickness and impurity concentration are used, then fabrication can proceed with standard processes, but precision variations occur and edge termination region length must be increased
Solution Approach 1:
By changing the thickness parameter to 0.7-1.1 μm and impurity concentration to 1×10^18/cm³ or less, the patent enhances the voltage withstanding capability per unit length of the FLR structure, allowing the edge termination region to be shortened while maintaining or improving precision.
3Strength
If the edge termination region is made longer to ensure voltage withstanding, then breakdown voltage is maintained, but device cost increases and reliability is reduced
Solution Approach 1:
The patent changes the impurity concentration parameter to 1×10^18/cm³ or less and thickness to 0.7-1.1 μm, which significantly enhances the voltage withstanding capability per unit length. This allows achieving the required breakdown voltage with a shorter edge termination region, thereby improving reliability by reducing the potential for defects in the extended region.
4Manufacturing precision
If thicker FLR structures with reduced impurity concentration are used, then precision and reliability are improved, but fabrication complexity increases
Solution Approach 1:
The patent specifies concrete parameter ranges (thickness: 0.7-1.1 μm, impurity concentration: 1×10^18/cm³ or less) that can be achieved through standard semiconductor fabrication processes like ion implantation and epitaxial growth, balancing precision improvement with fabrication feasibility.
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 improves the breakdown voltage and reliability of the semiconductor device by mitigating electric fields and reducing the length of the edge termination region, while simplifying the fabrication process.
Implementation Method 1
electric field concentrates in the edge termination region. Breakdown voltage of the semiconductor device is determined by an impurity concentration, thickness, and electric field strength
Implementation Method 2
a built-in parasitic diode (body diode) formed by pn junctions between an n−-type drift region and p-type base regions
Data Source
AI summary
A FLR structure is provided in an edge termination region as a voltage withstanding structure. The FLR structure is configured by multiple FLRs that concentrically surround a periphery of an active region. An impurity concentration of the FLRs is less than 1×1018/cm3 or preferably, may be in a range of 3×1017/cm3 to 9×1017/cm3. A thickness of each of the FLRs is in a range of 0.7 μm to 1.1 μm. A first interval between an innermost FLR and an outer peripheral pt-type region is at most about 1.2 μm.