Reverse Conducting IGBT Gate Interference Suppression

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Solution Overview

Problem

Reverse conducting IGBTs experience significant gate interference due to the integration of a diode structure, leading to fluctuations in forward voltage, which complicates control and increases costs when external circuits are used to mitigate this issue.

Innovation Solution

Incorporating a second conductivity type intermediate region between the emitter and emitter electrode in the semiconductor layer of the reverse conducting IGBT, forming a diode between this region and the emitter region, allows for the application of necessary forward voltage through a voltage drop, thereby inhibiting gate interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a diode structure is integrated into the semiconductor layer to enable reverse conduction, then the IGBT can function as a free wheeling diode, but gate interference occurs causing forward voltage to fluctuate largely

Engineering Contradiction:

Improvereverse conduction capabilityVSAvoidforward voltage stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

A second conductivity type intermediate region is introduced between the first conductivity type emitter region and the emitter electrode. This intermediate region acts as a mediator that forms a diode structure with the emitter region, enabling reverse conduction while the voltage drop across this diode ensures sufficient forward voltage is applied to suppress gate interference, thus stabilizing the forward voltage

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the electrical parameters of the semiconductor layer by introducing the intermediate region with different conductivity type and doping concentration. This parameter change creates a diode structure that modifies the voltage distribution, ensuring that when return current flows, the voltage drop across the new diode maintains sufficient forward voltage on the body region-drift region diode to prevent gate interference

Inventive Principle:

Principle #35Parameter changes

2Reliability

If an external circuit is provided to interrupt the gate signal when return current flows, then gate interference can be suppressed, but control becomes complicated and costs increase

Engineering Contradiction:

Improvegate interference suppressionVSAvoidcontrol circuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The semiconductor layer itself provides the solution by incorporating the intermediate region that automatically generates a diode structure. When return current flows through this diode, the voltage drop is automatically generated to suppress gate interference, eliminating the need for external detection and control circuits. The device serves itself to prevent gate interference through its internal structure

Inventive Principle:

Principle #25Self-service

3Productivity

If gate voltage is applied to the gate, then the IGBT can conduct current, but it becomes difficult for sufficient voltage to be applied in the forward direction of the diode structure

Engineering Contradiction:

Improvecurrent conduction capabilityVSAvoidforward voltage application

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The emitter region and emitter electrode are segmented by introducing the intermediate region between them. This segmentation creates a diode structure that can be independently biased. When the IGBT is on, the channel allows current flow while the diode structure formed by the segmented regions ensures proper voltage application in the forward direction, resolving the conflict between current conduction and voltage application

Inventive Principle:

Principle #1Segmentation

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 internal structural modification effectively reduces gate interference by ensuring consistent forward voltage application to the diode structure, improving the on-operation of the IGBT and reducing the need for external circuits, thus simplifying control and lowering costs.

Implementation Method 1

a diode is formed between the second conductivity type intermediate region and the first conductivity type emitter region. The necessary forward voltage is applied to the diode structure embedded between the body region and the drift region by a voltage drop of this diode

Methodology Applied

Scientific EffectDiode voltage drop: Diode

Data Source

PatentUS9099521B2Reverse conducting IGBT

Publication Date: 2015.08.04 DENSO CORP

AI summary

A reverse conducting IGBT that includes an insulated gate; a semiconductor layer having a first conductivity type drift region, a second conductivity type body region, a first conductivity type emitter region, and a second conductivity type intermediate region; and an emitter electrode provided on a surface of the semiconductor layer. The first conductivity type drift region of the semiconductor layer contacts the insulated gate. The second conductivity type body region of the semiconductor layer is provided on the drift region and contacts the insulated gate. The first conductivity type emitter region of the semiconductor layer is provided on the body region and contacts the insulated gate. The second conductivity type intermediate region of the semiconductor layer is provided on the emitter region and is interposed between the emitter region and the emitter electrode.