SiC JBS Diode Structure for Low Leakage and Surge Current
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices face issues with increased reverse leakage current due to high electric field strength at the contact surface, surge current leading to device destruction, and a trade-off between forward voltage and surge current capability, particularly in JBS structures.
Innovation Solution
The silicon carbide semiconductor device incorporates a novel structure with alternating p+-type regions at different depths in trenches, combined with nickel silicide films forming ohmic junctions, and a field limiting ring to enhance surge current capability and reduce forward voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a JBS structure with p+-type regions is adopted to reduce reverse leakage current, then reverse leakage current is reduced, but forward voltage increases and surge current capability decreases
Solution Approach 1:
The device segments the active region into multiple independent units by introducing trenches that divide the n-type drift region. Each segment contains p+-type regions forming pn junctions, while the trenches with Schottky barrier metal create Schottky barrier junctions. This segmentation allows current to be distributed across multiple paths, reducing the forward voltage drop while maintaining low reverse leakage current through the combined JBS structure.
Solution Approach 2:
The invention applies different junction types in different local regions: pn junctions are created in areas with p+-type regions for surge current handling, while Schottky barrier junctions are formed in trench areas for low reverse leakage. This local differentiation of junction qualities allows the device to optimize both forward voltage and reverse leakage characteristics in their respective regions.
2Object-generated harmful factors
If a JBS structure with p+-type regions is adopted to reduce reverse leakage current, then reverse leakage current is reduced, but surge current capability decreases
Solution Approach 1:
The device is divided into multiple segments by trenches, creating numerous independent current paths. The p+-type regions in each segment provide bipolar conduction capability for surge current, while the Schottky barrier regions maintain low reverse leakage. This segmented architecture enables the device to handle surge currents effectively without compromising reverse leakage performance.
Solution Approach 2:
The invention merges Schottky barrier junctions and pn junctions into a unified JBS structure where both junction types coexist and work together. The pn junctions provide surge current capability through bipolar conduction, while the Schottky barrier junctions provide low reverse leakage characteristics. This merging allows the device to simultaneously achieve both low reverse leakage and high surge current capability.
3Power
If the n−-type drift region is made thinner with higher impurity concentration to meet design specifications, then breakdown voltage is reduced to enable diode application, but surge current capability and heat dissipation performance worsen
Solution Approach 1:
The thinner n-type drift region is segmented into multiple sections by trenches, creating independent current paths. This segmentation compensates for the reduced thickness by increasing the number of parallel conduction channels, thereby maintaining surge current capability despite the thinner drift region design optimized for high breakdown voltage.
Solution Approach 2:
The invention creates local quality variations within the thin drift region by introducing p+-type regions and trenches at specific locations. The p+-type regions provide localized bipolar conduction for surge current handling, while the trench regions provide Schottky barrier junctions for voltage blocking. This local differentiation allows the thin drift region to simultaneously achieve high breakdown voltage and maintain surge current capability.
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 structure improves surge current capability and maintains low forward voltage by evenly distributing current and reducing local heat generation, ensuring efficient operation under surge conditions.
Implementation Method 1
a first silicide film provided on a corresponding one of the plurality of first second-conductivity-type regions with which a first ohmic junction is formed
Implementation Method 2
a plurality of Schottky regions, each of which is a region where the first electrode forms a Schottky barrier junction with the first-conductivity-type region
Data Source
AI summary
A silicon carbide semiconductor device includes an active region, a first-conductivity-type region, and a termination region. The active region has first second-conductivity-type regions and first silicide films in trenches, second second-conductivity-type regions and a second silicide film between the trenches that are adjacent to one another, and a first electrode while the termination region has a third second-conductivity-type region. The active region includes ohmic regions, non-operating regions and Schottky regions, each of which has a stripe shape. Each ohmic region is a region where the first electrode is in contact with either the first silicide film or the second silicide film. Each non-operating region is a region where the first electrode is in contact with either the first or second second-conductivity-type regions. Each Schottky region is a region where the first electrode forms a Schottky barrier junction with the first-conductivity-type region.