SiC JBS Diode Wave-Shaped P+ Regions for Lower Reverse Leakage
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Solution Overview
Problem
Silicon carbide (SiC) Junction Barrier Schottky (JBS) diodes face challenges with high reverse leakage current due to electric field at the metal-semiconductor interface, which increases with voltage, and prior designs to mitigate this often result in increased on-resistance and forward voltage drop.
Innovation Solution
A SiC JBS diode structure with serpentine or wave-shaped P+ regions and strategically placed P+ island regions reduces the electric field at the Schottky metal interface during reverse bias without significantly impacting forward bias performance, using heavily-doped P+ regions and large P+ island regions to manage surge currents effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If isolated P+N junctions are placed within the active area of the SBD to reduce reverse leakage current, then reverse leakage current is reduced, but the overall area of the diode increases and specific on-resistance increases
Solution Approach 1:
The patent divides the P-type region into multiple isolated P+ islands distributed within the N-type drift region rather than using a continuous P-type layer. This segmentation allows the P-type regions to terminate electric field lines effectively while minimizing the total area occupied by P-type material, thus reducing reverse leakage without significantly increasing diode area or on-resistance
Solution Approach 2:
The patent creates local P+ doped regions with high doping concentration specifically positioned to terminate electric field lines at the metal-semiconductor interface. These localized P-type regions provide the necessary field termination function only where needed, rather than throughout the entire device structure, optimizing the balance between leakage reduction and area utilization
2Object-generated harmful factors
If P+N junctions are inserted to reduce surface electric field and lower reverse leakage current, then reverse leakage current is reduced, but capacitance in reverse bias increases
Solution Approach 1:
By segmenting the P-type region into discrete islands rather than using continuous P-type material, the total junction area is reduced. This segmentation decreases the total capacitance formed by P-N junctions while maintaining sufficient field termination capability through strategic positioning of the P+ islands at the metal-semiconductor interface
3Reliability
If hexagonal shaped P-type regions are used to mitigate current surge, then surge current protection is improved, but on-resistance increases at low currents and forward voltage drop increases
Solution Approach 1:
The patent implements local P+ doped regions with high doping concentration specifically where needed to protect against surge currents at the metal-semiconductor interface. These localized regions provide surge protection without creating extensive P-type areas that would increase on-resistance and forward voltage drop. The high doping concentration in the P+ regions ensures low resistance when conducting surge currents while minimizing impact on normal operating conditions
Solution Approach 2:
The patent uses high doping concentration (P+ regions) in the protective regions to create low resistance paths for surge currents. By changing the doping parameter to very high levels in specific locations, the regions can handle surge currents effectively while maintaining low on-resistance during normal operation, avoiding the trade-off present in lower-doping hexagonal designs
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 proposed diode structure achieves reduced reverse leakage current, lower forward voltage drop, and enhanced surge current handling capabilities, protecting the device from potential damage while maintaining low on-resistance.
Implementation Method 1
many of the electric field lines reaching the surface terminate on P+N junctions rather than on the Schottky barrier junction, thus reducing the surface electric field and hence lowering the reverse leakage current
Implementation Method 2
The leakage is due to electrons that enter the semiconductor material from the metal by thermionic-field emission (TFE) under reverse bias
Implementation Method 3
various designs have been adopted that turn on the P+N junctions, resulting in the injection of minority carriers into the N-type drift layer, which reduces the power dissipated in the device
Data Source
AI summary
A Junction Barrier Schottky (JBS) diode includes an N-type epitaxial layer disposed on SiC substrate, P+ wavy regions are disposed in the epitaxial layer adjoining a top planar surface, each of which is separated from an adjacent one of the wavy regions by a Schottky barrier contact region. P+ island regions are disposed in the Schottky barrier contact regions. A top metal layer is disposed along the top planar surface in direct contact with the Schottky barrier contact regions, the P+ wavy regions, and the P+ island regions, the top metal layer comprising the anode of the JBS diode. A bottom metal layer is disposed beneath the SiC substrate. The bottom metal layer comprises the cathode of the JBS diode.