Trench Semiconductor Edge Termination Graded Doping
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Solution Overview
Problem
In semiconductor power applications, insulated gate field effect transistors (IGFETs) face a trade-off between breakdown voltage and on-resistance, with charge compensation by field plates in the edge termination area limiting the breakdown voltage margin.
Innovation Solution
A semiconductor device with a trench structure featuring a gate electrode and field electrodes, where the body region's doping concentration is lowered at the lateral end of the pn junction in the edge termination area compared to the transistor cell area, enhancing the breakdown voltage while maintaining a high packing density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If field plates are added in the edge termination area to improve breakdown voltage, then breakdown voltage is improved, but on-resistance increases
Solution Approach 1:
The patent applies local quality by implementing a graded doping profile specifically in the edge termination area. The doping concentration is reduced laterally from the transistor cell area toward the edge termination area, creating a gradual transition zone. This localized modification allows the edge termination region to sustain higher breakdown voltages without significantly increasing the overall on-resistance, as the lower doping concentration is confined to the edge region rather than the entire device structure.
2Reliability
If trench structure with field electrodes is used to increase packing density, then on-resistance is reduced, but breakdown voltage margin is limited
Solution Approach 1:
The patent combines the trench structure with field electrodes for high packing density and low on-resistance, while simultaneously applying a graded doping profile in the edge termination area to compensate for the limited breakdown voltage margin. The localized doping reduction at the edges creates a field distribution that enhances breakdown voltage without disrupting the benefits of the trench structure in the transistor cell area.
Data Source
AI summary
A semiconductor device includes a semiconductor body having a semiconductor substrate of a first conductivity type and a semiconductor layer of the first conductivity type on the substrate. A trench structure extends into the semiconductor body from a first surface and includes a gate electrode and at least one field electrode arranged between the gate electrode and a bottom side of the trench structure. A body region adjoins the trench structure and laterally extends from a transistor cell area into an edge termination area. A pn junction is between the body region and semiconductor layer. A doping concentration of at least one of the body region and semiconductor layer is lowered at a lateral end of the pn junction in the edge termination area compared to a doping concentration of the at least one of the body region and semiconductor layer at the pn junction in the transistor cell area.