SiC Trench Gate Diode Region for High Voltage Protection
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Solution Overview
Problem
Power transistors with high voltage blocking capabilities face issues due to insufficient dielectric strength of the gate dielectric, leading to breakdown under high electric fields, and integrated body diodes often have lower current ratings than desired.
Innovation Solution
A semiconductor device design with a trench structure where the gate electrode is dielectrically insulated from the body, diode, and drift regions, and a diode region with a lower diode region below the trench having a maximum doping concentration distant from the trench bottom, effectively protecting the gate electrode from high electric fields and enhancing diode current rating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high blocking voltages are implemented in power transistors, then voltage blocking capability is improved, but the gate dielectric may breakdown due to high electric fields
Solution Approach 1:
A field plate structure is introduced as an intermediary element between the gate electrode and the high voltage regions. The field plate extends over the drift region and is connected to the gate, creating a gradual voltage transition zone that reduces the electric field intensity at critical interfaces, thereby protecting the gate dielectric from breakdown while maintaining high blocking voltage capability
Solution Approach 2:
The electric field distribution is modified by changing the geometric parameters of the gate structure. By extending the gate electrode into a field plate configuration and adjusting its length and position over the drift region, the voltage gradient is softened, transforming the abrupt high-field region into a more distributed, lower-intensity field profile that the gate dielectric can withstand
2Adaptability or versatility
If the body diode is used for parallel connection to load path, then diode function is provided, but the current rating is lower than desired
Solution Approach 1:
The diode function is segmented from the transistor body structure. Instead of relying solely on the body diode formed by the body-drift region junction, a separate dedicated diode structure is created with its own optimized doping profile and geometry, allowing the diode current path to be independent and scaled separately from the transistor channel dimensions
Solution Approach 2:
The diode structure is extended into the vertical dimension by creating a deep diode region that reaches into the drift region. This vertical extension provides additional cross-sectional area for current flow, effectively increasing the current rating by utilizing the third dimension rather than being constrained to the planar body diode configuration
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 protects the gate dielectric from high electric fields and provides a diode with high current rating and low losses, improving the overall performance of the semiconductor device.
Implementation Method 1
A gate electrode of the at least one device cell is arranged in the trench and dielectrically insulated from the body region, the diode region and the drift region by a gate dielectric
Data Source
AI summary
A semiconductor device includes a SiC body having a first surface, a gate trench extending from the first surface into the SiC body and having a first sidewall, a second sidewall opposite the first sidewall, and a bottom, a source region of a first conductivity type formed in the SiC body and adjoining the first sidewall of the gate trench, a drift region of the first conductivity type formed in the SiC body below the source region, a body region of a second conductivity type formed in the SiC body between the source region and the drift region and adjoining the first sidewall of the gate trench, and a diode region of the second conductivity type formed in the SiC body and adjoining the second sidewall and the bottom of the gate trench but not the first sidewall of the gate trench.