Bidirectional Trench FET Gate-Based Resurf Design
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Solution Overview
Problem
Trench FET devices typically fail to provide bidirectional blocking capabilities without compromising breakdown voltage or increasing on-state resistance, as improving breakdown voltage in one direction often results in lower breakdown voltage in the other direction and increased on-state resistance.
Innovation Solution
The implementation of a recessed gate structure with a reduced surface field (RESURF) effect, where the gate structure is positioned alongside the drift region to reduce electric field magnitudes, optimizing the reverse breakdown voltage without adverse effects on on-state resistance or forward breakdown voltage, achieved through careful recess distance selection and etch procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the distance between source and drain electrodes is increased to improve breakdown voltage, then breakdown voltage is improved, but on-state resistance increases due to longer conduction path
Solution Approach 1:
The gate structure is recessed to a specific depth within the drift region, creating different functional zones: the upper portion provides high-voltage blocking through the RESURF effect, while the lower portion maintains low resistance conduction. This localized structural modification allows different regions to optimize for different functions simultaneously.
Solution Approach 2:
Instead of extending the gate to the surface (conventional approach), the gate is recessed into the drift region. This inverted configuration reduces the electric field magnitude at the surface through the RESURF effect, improving breakdown voltage without requiring increased source-drain distance that would raise on-state resistance.
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
This approach enhances the reverse breakdown voltage while maintaining optimal on-state resistance and forward breakdown voltage, providing improved bidirectional blocking capabilities without increasing fabrication costs or modifying existing device design features.
Implementation Method 1
The gate structure and the gate dielectric layer have a substantial vertical overlap with the drift region such that electric field magnitudes in the drift region are reduced through application of the control voltage
Data Source
AI summary
A device includes a semiconductor substrate having a surface, a trench in the semiconductor substrate extending vertically from the surface, a body region laterally adjacent the trench, spaced from the surface, having a first conductivity type, and in which a channel is formed during operation, a drift region between the body region and the surface, and having a second conductivity type, a gate structure disposed in the trench alongside the body region, recessed from the surface, and configured to receive a control voltage is applied to control formation of the channel, and a gate dielectric layer disposed along a sidewall of the trench between the gate structure and the body region. The gate structure and the gate dielectric layer have a substantial vertical overlap with the drift region such that electric field magnitudes in the drift region are reduced through application of the control voltage.