Reverse-conducting MOS Device with Variable Lateral Doping

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Solution Overview

Problem

Reverse-conducting IGBT devices face challenges with snap-back effects and thermal performance due to high voltage drop across the drift layer, leading to reduced safe operating area (SOA) and potential device destruction during reverse recovery.

Innovation Solution

Incorporating a variable-lateral-doping (VLD) layer and a highly doped protection layer with ring-shaped regions surrounding the active cell region, which reduces the electric field and spreads hole current, preventing localized temperature peaks and enhancing turn-off capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a reverse-conducting IGBT device is designed with a drift layer for high voltage operation, then the breakdown voltage is improved, but the voltage drop across the drift layer increases causing snap-back effects and reduced safe operating area

Engineering Contradiction:

Improvebreakdown voltageVSAvoidvoltage drop and snap-back effects

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The drift layer is segmented into multiple regions with different doping concentrations. The upper drift layer has a first doping concentration while the lower drift layer has a second doping concentration, creating distinct zones that manage voltage distribution and reduce snap-back effects during reverse recovery

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the drift layer are assigned different doping concentrations to optimize local performance. The upper region with lower doping concentration handles high voltage blocking, while the lower region with higher doping concentration reduces on-state voltage drop and improves turn-off capability

Inventive Principle:

Principle #3Local quality

2Reliability

If the drift layer thickness is increased to handle higher voltages, then the breakdown voltage is improved, but the voltage drop and power losses increase

Engineering Contradiction:

Improvebreakdown voltageVSAvoidvoltage drop and power losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The drift layer employs a non-uniform doping profile with different concentrations at different depths. This local variation in doping quality allows the structure to simultaneously achieve high voltage blocking capability through increased effective thickness while maintaining lower on-state resistance through the higher doped lower region

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The drift layer functions as a composite structure with two distinct doping regions, combining the advantages of low-doped material (high breakdown voltage) and high-doped material (low on-state resistance) within a single continuous layer

Inventive Principle:

Principle #40Composite materials

3Adaptability or versatility

If the device operates in diode mode with high current, then the reverse conducting capability is improved, but localized temperature peaks occur reducing the safe operating area

Engineering Contradiction:

Improvereverse conducting capabilityVSAvoidlocalized temperature peaks

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The non-uniform doping profile creates regions with different electrical and thermal properties. The lower drift layer region with higher doping concentration serves as a thermal management zone that dissipates heat more effectively, preventing localized temperature peaks during high-current reverse recovery operations

Inventive Principle:

Principle #3Local quality

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 configuration significantly reduces peak temperatures and improves the safe operating area (SOA) of the device by distributing hole current and reducing electric field concentration, thereby enhancing turn-off capability and thermal performance.

Implementation Method 1

reduces the electric field and spreads hole current, preventing localized temperature peaks

Methodology Applied

Scientific EffectElectric field: Electric Field

Implementation Method 2

spreads hole current, preventing localized temperature peaks

Methodology Applied

Scientific EffectCharge carrier conduction: Conduction (electrical)

Data Source

PatentEP3238260B1Reverse-conducting semiconductor device

Publication Date: 2020.03.25 ABB POWER GRIDS SWITZERLAND AG

Figure 1~2
Figure 3~4
Figure 5~6

AI summary

A reverse-conducting MOS device (1) is provided having an active cell region (10) and a termination region (12). Between a first and second main side (20, 25). The active cell region (10) comprises a plurality of MOS cells (11) with a base layer (4) of a second conductivity type. On the first main side (20) a bar (8) of the second conductivity type, which has a higher maximum doping concentration than the base layer (4), is arranged between the active cell region (10) and the termination region (12), wherein the bar (8) is electrically connected to the first main electrode (2). On the first main side (20) in the termination region (12) a variable-lateral-doping layer (7) of the second conductivity type is arranged. A protection layer (9) of the second conductivity type is arranged in the variable-lateral-doping layer (7), which protection layer (9) has a higher maximum doping concentration than the maximum doping concentration of the variable-lateral-doping layer in a region attached to the protection layer (9).