Reverse Conducting IGBT Collector Doping for Lower Switching Loss

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Solution Overview

Problem

The increase in recovery current and switching loss in reverse conducting Insulated Gate Bipolar Transistors (IGBTs) due to oblique injection of holes during recovery operation is a challenge.

Innovation Solution

A semiconductor device with a boundary region between the IGBT and diode regions, featuring a collector layer with varying impurity concentration, where the boundary region has a lower concentration of the second conductivity type impurity, suppressing oblique hole injection and reducing switching losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a boundary region is introduced between IGBT and diode regions, then oblique hole injection is suppressed and switching loss is reduced, but device structure becomes more complex

Engineering Contradiction:

Improveswitching lossVSAvoiddevice structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The collector layer is segmented into two distinct regions: a first collector layer in the IGBT region and a second collector layer in the boundary region. This segmentation allows different impurity concentrations in different areas, suppressing oblique hole injection from the diode region into the IGBT region while maintaining the benefits of the boundary region structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by creating a boundary region with specific characteristics between the IGBT and diode regions. The second collector layer in the boundary region has a lower concentration of second conductivity type impurity compared to the first collector layer, providing localized properties that suppress harmful oblique hole injection while maintaining overall device functionality.

Inventive Principle:

Principle #3Local quality

2Loss of energy

If the concentration of second conductivity type impurity is reduced in the boundary region, then oblique hole injection is suppressed, but manufacturing precision requirements increase

Engineering Contradiction:

Improverecovery lossVSAvoidimpurity concentration control

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The patent changes the impurity concentration parameter by creating a second collector layer with a lower concentration of second conductivity type impurity in the boundary region compared to the first collector layer in the IGBT region. This parameter change effectively suppresses oblique hole injection and reduces recovery loss, though it does require precise control during manufacturing.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20260047118A1Semiconductor device and method of manufacturing the same

Publication Date: 2026.02.12 DENSO CORP

AI summary

A semiconductor substrate of a reverse conducting IGBT includes a collector layer in contact with a collector electrode, within an IGBT region and a boundary region. The collector layer has a first collector layer provided in the IGBT region and a second collector layer provided in the boundary region. The second collector layer has a lower impurity concentration than the first collector layer.