Trench Gate Semiconductor Device for dv/dt Control
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Solution Overview
Problem
Conventional IGBT structures face challenges in controlling the time rate of change of output voltage dv/dt during turn-on switching periods while maintaining low loss and high breakdown voltage, with existing solutions either increasing power loss or compromising breakdown voltage.
Innovation Solution
The semiconductor device features trench gates with embedded electrodes connected to the emitter electrode, creating narrow and wide distance regions with channel regions in the trenches, which reduces feedback capacity and maintains high breakdown voltage, enabling improved dv/dt controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a floating-p layer is provided between trenches to improve avalanche capability and lower ON-voltage, then breakdown voltage is maintained, but dv/dt controllability is reduced during turn-on switching
Solution Approach 1:
The patent removes the floating-p layer from the structure between trenches. This extraction eliminates the source of displacement current that causes uncontrollable dv/dt, while the damage-free p-n junction between the n-type buffer layer and n--type drift layer maintains adequate avalanche capability without the harmful floating-p layer
Solution Approach 2:
The patent creates different functional regions: narrow distance portions between adjacent trenches maintain low ON-voltage through p-type channel layers, while wide distance portions are left as insulation films without floating-p layers. This local differentiation allows dv/dt controllability in wide portions while maintaining electrical performance in narrow portions
2Loss of energy
If the distance between trenches is reduced to lower ON-voltage, then conduction loss is reduced, but breakdown voltage decreases
Solution Approach 1:
The patent implements narrow distance portions between adjacent trenches for low ON-voltage operation, while wide distance portions are maintained as insulation regions. This spatial differentiation allows the device to achieve low conduction loss through narrow channels while maintaining breakdown voltage through wide insulation spacing
Solution Approach 2:
The patent transitions from a uniform one-dimensional trench spacing to a two-dimensional structure with both narrow and wide distance portions. This dimensional change enables simultaneous optimization of conduction paths (narrow regions) and breakdown performance (wide regions) in different spatial locations
3Ease of operation
If gate resistance is increased to control dv/dt, then voltage rate of change is reduced, but switching speed decreases
Solution Approach 1:
By removing the floating-p layer, the patent eliminates the displacement current path through the gate insulation film. This extraction makes dv/dt independent of gate resistance effects, allowing dv/dt control without the trade-off of reduced switching speed that plagues conventional designs
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 configuration reduces feedback capacity, maintains low loss and high breakdown voltage, and enhances dv/dt controllability during the turn-on switching period, as demonstrated by improved collector-emitter voltage waveforms and breakdown voltage calculations.
Implementation Method 1
a displacement current flows into a gate electrode 110 via a feedback capacity formed with a gate insulation film 109
Implementation Method 2
a p-n junction formed with the floating-p layer 105 and an n−-type drift layer 104 relaxes the electric field applied to corner portions of the trenches 117
Data Source
AI summary
It is intended to provide a semiconductor device capable to improve a controllability of dv/dt by a gate drive circuit during a turn-on switching period, while maintaining a low loss and a high breakdown voltage. Trench gates are disposed so as to have narrow distance regions and wide distance regions, wherein each of the narrow distance regions is provided with a channel region, and each of the wide distance regions is provided with trenches, each trench having an electrode electrically connected to the emitter electrode. In this manner, even if a floating-p layer is removed, it is possible to reduce a feedback capacity and maintain a breakdown voltage.