RC-IGBT Plug Region Layout for Lower Forward Voltage and Recovery Loss

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Solution Overview

Problem

Existing semiconductor devices face challenges in optimizing the trade-off between reducing forward voltage and reverse recovery loss, particularly in reverse conducting IGBTs, due to the design of trench contact portions and plug regions.

Innovation Solution

The semiconductor device incorporates a trench contact portion in the mesa portion of the transistor region and a plug region with specific doping concentrations and configurations, including a first plug region covering the trench contact portion's bottom and a second plug region with selective placement, to enhance hole extraction and reduce latch-up while minimizing forward voltage and reverse recovery loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a trench contact portion is provided in each mesa portion with a plug region at the bottom, then contact resistance is reduced and current conduction is improved, but the forward voltage increases and reverse recovery loss increases

Engineering Contradiction:

Improvecontact resistanceVSAvoidreverse recovery loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The plug region is segmented into multiple doping concentration zones (first plug region with higher doping concentration and second plug region with lower doping concentration). This segmentation allows the high-doping first plug region to reduce contact resistance while the low-doping second plug region reduces reverse recovery loss, resolving the contradiction between contact resistance and reverse recovery loss

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the plug structure are assigned different doping concentrations to optimize local functions. The first plug region near the trench contact portion uses high doping concentration for low contact resistance, while the second plug region extends into the drift region with lower doping concentration to minimize reverse recovery loss, achieving local optimization of both parameters

Inventive Principle:

Principle #3Local quality

2Loss of energy

If the doping concentration in the plug region is increased to reduce reverse recovery loss, then reverse recovery loss decreases, but forward voltage increases

Engineering Contradiction:

Improvereverse recovery lossVSAvoidforward voltage

Core Design Contradiction:

Loss of energyVSUse of energy by moving object

Solution Approach 1:

The plug region employs non-uniform doping concentration distribution with a first plug region having higher doping concentration for low reverse recovery loss and a second plug region with lower doping concentration to maintain low forward voltage. This local quality differentiation resolves the contradiction between reverse recovery loss and forward voltage

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The plug region is divided into multiple segments with different doping concentrations. The first plug region segment provides low reverse recovery loss while the second plug region segment maintains low forward voltage, allowing both contradictory requirements to be satisfied simultaneously through segmented structure

Inventive Principle:

Principle #1Segmentation

3Loss of energy

If the trench contact portion is removed from the diode portion to reduce reverse recovery loss, then reverse recovery loss decreases, but forward voltage increases

Engineering Contradiction:

Improvereverse recovery lossVSAvoidforward voltage

Core Design Contradiction:

Loss of energyVSUse of energy by moving object

Solution Approach 1:

Instead of removing the trench contact portion from the diode portion (which would increase forward voltage), the invention inverts the approach by providing a selectively doped second plug region in the drift region that extends laterally. This inverted structure achieves low reverse recovery loss without requiring trench contact portions in the diode portion, while maintaining low forward voltage through the optimized plug region doping profile

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS20250212436A1Semiconductor device

Publication Date: 2025.06.26 FUJI ELECTRIC CO LTD

AI summary

Provided is a semiconductor device with a transistor portion and a diode portion, including a drift region of a first conductivity type and a front surface side electrode provided above a semiconductor substrate. The transistor portion may have a base region of a second conductivity type provided above the drift region; a trench contact portion provided on a front surface of the semiconductor substrate; and a first plug region of a second conductivity type with a higher doping concentration than the base region, under the trench contact portion. The diode portion may have an anode region of a second conductivity type provided above the drift region; and a second plug region of a second conductivity type with a higher doping concentration than the anode region. The second plug region may contact the front surface side electrode in a position shallower than the first plug region.