SiC Power Transistor Diode Field Stop Protection
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Solution Overview
Problem
Power transistors with high voltage blocking capabilities face issues due to high electric fields at the pn-junction between the body and drift regions, leading to potential gate dielectric breakdown, and existing body diodes often have lower current ratings than required.
Innovation Solution
The semiconductor device incorporates diode regions with varying doping concentrations and rounded corners in trenches to protect the gate electrode from high electric fields, allowing for a high current rating and low losses by forming a JFET that pinches off channel regions to prevent further field strength increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high voltage blocking capability is implemented in power transistors, then voltage blocking capability is improved, but high electric fields at the pn-junction cause gate dielectric breakdown
Solution Approach 1:
A field stop region is introduced as an intermediary between the body region and the drift region. This field stop region with higher doping concentration than the drift region acts as a mediator to shape and limit the electric field distribution, preventing excessive field strength at the pn-junction interface while maintaining the high voltage blocking capability of the device.
Solution Approach 2:
The field stop region is created with a specific local doping concentration that is higher than the surrounding drift region but lower than the body region. This local variation in doping quality allows the electric field to be controlled specifically at the critical junction area without affecting the overall voltage blocking characteristics of the device.
2Adaptability or versatility
If body diode is used for parallel connection to load path, then diode function is provided, but current rating is lower than desired
Solution Approach 1:
The device structure is segmented to include separate functional regions: the body diode formed by the body-drift junction and an additional diode structure created by the field stop region. This segmentation allows the diode function to be distributed and enhanced, providing higher current rating capability while maintaining the required diode functionality for parallel connection to the load path.
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 effectively protects the gate dielectric from high electric fields and enhances the current rating of the diode, ensuring reliable voltage blocking capabilities with low losses, particularly suitable for high-voltage SiC-based semiconductor devices.
Implementation Method 1
The body diode is formed by a pn junction between the body region and the drift region
Implementation Method 2
a gate dielectric dielectrically insulating the gate electrode from the semiconductor body
Data Source
AI summary
A semiconductor body having a drift region layer, a body region layer adjoining the drift region layer, and a source region layer adjoining the body region layer and forming a first surface of the semiconductor body is provided. At least two trenches extend from the first surface of the semiconductor body through the source region layer and the body region layer. In each of the trenches a gate electrode and a gate dielectric are formed. Diode regions are directly adjacent to each of the at least two trenches. The diode regions extend from the first surface of the semiconductor body through the source region layer and the body region layer. The diode regions include a first region and a second region. A doping concentration in the diode regions varies such that a doping concentration is higher near the first surface than at the bottom of the trench.