IGBT Dummy Gate Electrode Segmentation for Switching Loss

Solution Overview

Problem

Trench type IGBTs face challenges in achieving low on-state voltage, high breakdown voltage, and soft switching characteristics while minimizing switching loss and electromagnetic noise, due to trade-offs between these parameters and the inhomogeneous electric field distribution in silicon substrates.

Innovation Solution

The semiconductor device incorporates a semiconductor substrate with a drift layer and base layer divided by trenches, featuring a channel layer and float layer arrangement with a specific ratio, where the dummy gate electrode is electrically connected to a float layer and isolated from another float layer, allowing for balanced switching surge voltage and loss, and homogeneous operation to enhance breakdown voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the dummy gate electrode is connected to the gate electrode, then the electric potential is stabilized, but the capacitance between gate and collector increases causing large switching loss

Engineering Contradiction:

Improveelectric potential stabilityVSAvoidswitching loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The invention segments the gate electrode system into two independent parts: the gate electrode (104) for controlling the active channel and the dummy gate electrode (106) for stabilizing electric potential in the dummy trench (103). By separating their functions and connections, the patent eliminates the parasitic capacitance between dummy gate and collector that would occur if they were connected, thereby reducing switching loss while maintaining potential stability through the dummy trench structure itself.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention extracts the dummy gate electrode (106) from the functional gate control system and isolates it electrically from the collector. The dummy gate electrode is left floating or connected only to the emitter, removing it from the high-voltage switching path. This extraction eliminates the harmful capacitance effect while preserving the dummy trench's beneficial role in electric field distribution and breakdown voltage enhancement.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If the dummy gate electrode is connected to the emitter electrode, then the electric potential is stabilized, but the capacitance between gate and emitter increases causing large switching surge voltage

Engineering Contradiction:

Improveelectric potential stabilityVSAvoidswitching surge voltage

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention segments the gate electrode system into two independent parts: the gate electrode (104) for controlling the active channel and the dummy gate electrode (106) for stabilizing electric potential in the dummy trench (103). By separating their functions and connections, the patent eliminates the parasitic capacitance between dummy gate and collector that would occur if they were connected, thereby reducing switching loss while maintaining potential stability through the dummy trench structure itself.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention extracts the dummy gate electrode (106) from the functional gate control system and isolates it electrically from the collector. The dummy gate electrode is left floating or connected only to the emitter, removing it from the high-voltage switching path. This extraction eliminates the harmful capacitance effect while preserving the dummy trench's beneficial role in electric field distribution and breakdown voltage enhancement.

Inventive Principle:

Principle #2Taking out (Extraction)

3Object-affected harmful factors

If the gate resistance is increased to reduce electromagnetic noise, then the voltage drop speed is reduced, but the switching loss increases

Engineering Contradiction:

Improveelectromagnetic noiseVSAvoidswitching loss

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The invention introduces the dummy trench (103) with its dummy gate electrode (106) as an intermediary structure between the active channel and the collector region. This dummy structure acts as a buffer that smooths the electric field distribution during switching transitions, reducing the dvdt and thereby suppressing electromagnetic noise without requiring increased gate resistance, thus avoiding the associated switching loss penalty.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS7977704B2Semiconductor device having insulated gate semiconductor element, and insulated gate bipolar transistor

Publication Date: 2011.07.12 FUJI ELECTRIC CO LTD

AI summary

A semiconductor device having an IGBT includes: a substrate; a drift layer and a base layer on the substrate; trenches penetrating the base layer to divide the base layer into base parts; an emitter region in one base part; a gate element in the trenches; an emitter electrode; and a collector electrode. The one base part provides a channel layer, and another base part provides a float layer having no emitter region. The gate element includes a gate electrode next to the channel layer and a dummy gate electrode next to the float layer. The float layer includes a first float layer adjacent to the channel layer and a second float layer apart from the channel layer. The dummy gate electrode and the first float layer are coupled with a first float wiring on the base layer. The dummy gate electrode is isolated from the second float layer.