SiC Schottky Rectifier Termination for Avalanche Robustness
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Solution Overview
Problem
High voltage silicon carbide (SiC) Schottky-barrier power rectifiers face issues with excessive currents during avalanche conditions, leading to potential destruction due to insufficient robustness in the termination region.
Innovation Solution
The design incorporates a drift region of a first conductivity type, a shielding body, and a Schottky region with a termination region having multiple zones, including a transition zone with a recess, to enhance avalanche robustness. This configuration includes a rim of a second conductivity type surrounding the shielding body and termination region, with specific doping and metal contact arrangements to manage electric fields and reduce leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional termination region design is used in SiC Schottky-barrier power rectifiers, then the device structure is simple, but excessive currents occur under avalanche conditions leading to device destruction
Solution Approach 1:
The termination region is segmented into multiple zones with different doping concentrations (first zone with higher doping, second zone with lower doping). This segmentation allows each zone to handle different aspects of the electric field distribution, preventing excessive current concentration and improving avalanche robustness without requiring completely new device structures
Solution Approach 2:
Different regions of the termination structure are given different doping characteristics - the first zone has higher doping concentration while the second zone has lower doping concentration. This local quality variation optimizes the electric field distribution in different areas, allowing the device to withstand avalanche conditions while maintaining a manageable overall structure
2Reliability
If the termination region is designed to handle avalanche conditions, then device reliability improves, but manufacturing complexity increases due to multiple zones and doping variations
Solution Approach 1:
The termination region is divided into manufacturable zones with distinct doping profiles. The first zone and second zone can be formed using sequential doping processes or implantation techniques that are compatible with existing SiC fabrication workflows, balancing reliability improvement with manufacturing feasibility
Solution Approach 2:
The doping concentration parameter is varied across different zones of the termination region. By controlling doping parameters (concentration, depth, distribution) in the first and second zones, the device achieves enhanced avalanche robustness through parameter optimization rather than structural 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 provides improved avalanche robustness, preventing early destruction and maintaining stable breakdown voltage and on-state voltage under repetitive avalanche conditions, allowing the SiC device to sustain high avalanche currents without failure.
Implementation Method 1
excessive currents can occur in a termination region under avalanche conditions
Implementation Method 2
manage electric fields and reduce leakage currents
Implementation Method 3
a rim having a second conductivity type at least partially surrounding the shielding body and the Schottky region. The SiC device can include a termination region at least partially surrounding the rim and having a doping of the second conductivity type
Data Source
AI summary
In at least one general aspect, a SiC device can include a drift region of a first conductivity type, a shielding body, and a Schottky region. The SiC device can include a rim having a second conductivity type at least partially surrounding the shielding body and the Schottky region. The SiC device can include a termination region at least partially surrounding the rim and having a doping of the second conductivity type. The termination region can have a transition zone disposed between a first zone and a second zone where the first zone has a top surface lower in depth than a depth of a top surface of the second zone and the transition zone has a recess.