IGBT Trench Gate Segmentation for Switching Loss Reduction

Solution Overview

Problem

Insulated gate bipolar transistors (IGBTs) with trench gate structures face significant switching losses due to delayed carrier storage and discharge during state transitions, leading to increased ON resistance and switching time.

Innovation Solution

The IGBT design incorporates a two-stage structure with a gate electrode and a first field plate electrode, where the gate electrode is insulated from the trench gate structure, reducing the gate-collector capacitance and enhancing carrier discharge efficiency, thereby minimizing switching losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If a trench gate structure extending deeply into the n--type base layer is used, then ON resistance is reduced, but switching loss increases

Engineering Contradiction:

Improvetrench gate depthVSAvoidswitching loss

Core Design Contradiction:

Length of stationary objectVSLoss of energy

Solution Approach 1:

The gate structure is segmented into two distinct parts: a first gate electrode extending into the n--type base layer for conductivity modulation, and a second gate electrode positioned above it for carrier discharge control. This segmentation allows each gate to perform its specific function optimally, reducing the trade-off between ON resistance and switching loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A lightly-doped n-type layer is introduced as an intermediary between the first and second gates, and between the gates and the n--type base layer. This intermediary layer facilitates controlled carrier discharge while maintaining the deep trench structure's ability to reduce ON resistance, effectively mediating between the conflicting requirements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a trench gate structure extending deeply into the n--type base layer is used, then carrier confinement is improved, but carrier discharge time increases

Engineering Contradiction:

Improvecarrier confinementVSAvoidcarrier discharge time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The gate structure is segmented into two distinct parts: a first gate electrode extending into the n--type base layer for conductivity modulation, and a second gate electrode positioned above it for carrier discharge control. This segmentation allows each gate to perform its specific function optimally, reducing the trade-off between ON resistance and switching loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The dual gate structure enables dynamic control of carrier discharge by applying different voltages to the first and second gates independently. The second gate can be used to accelerate carrier discharge during turn-off while the first gate maintains the deep confinement needed for low ON resistance during conduction.

Inventive Principle:

Principle #15Dynamics

3Power

If a trench gate structure extending deeply into the n--type base layer is used, then conductivity modulation is enhanced, but switching speed decreases

Engineering Contradiction:

Improveconductivity modulationVSAvoidswitching speed

Core Design Contradiction:

PowerVSSpeed

Solution Approach 1:

The gate structure is segmented into two distinct parts: a first gate electrode extending into the n--type base layer for conductivity modulation, and a second gate electrode positioned above it for carrier discharge control. This segmentation allows each gate to perform its specific function optimally, reducing the trade-off between ON resistance and switching loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second gate electrode can be used to preliminarily discharge carriers from the n--type base layer before the main switching action, thereby preparing the device for faster switching. This preliminary action reduces the carrier storage that would otherwise slow down the switching process while maintaining effective conductivity modulation during the ON state.

Inventive Principle:

Principle #10Preliminary action

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 design significantly reduces switching losses by shortening the time required for carrier discharge and storage, resulting in lower ON resistance and faster switching times compared to traditional trench gate structures.

Implementation Method 1

the gate electrode is insulated from the trench gate structure, reducing the gate-collector capacitance

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS10439054B2Insulated gate bipolar transistor

Publication Date: 2019.10.08 KK TOSHIBA

AI summary

According to one embodiment, an IGBT has a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, a third semiconductor layer of the second conductivity type, a fourth semiconductor layer of the first conductivity type, and a fifth semiconductor layer of the second conductivity type, between a first electrode and a second electrode, on the first electrode in order. A third electrode is provided on the third semiconductor layer, the fourth semiconductor layer, and the fifth semiconductor layer via a gate insulating film, and is insulated from the first electrode and the second electrode. A fourth electrode is provided between the third electrode and the second semiconductor layer, and is insulated from the third electrode and the second semiconductor layer.