Superjunction Power Device Pillar Segmentation

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Solution Overview

Problem

Power semiconductor devices face challenges in optimizing on-resistance and breakdown voltage while maintaining low switching speed, particularly for applications above 400 volts, where IGBTs offer lower on-resistance but slower switching speed compared to power MOSFETs, and existing charge balancing structures have limited success in addressing these competing performance requirements.

Innovation Solution

The development of a power device with alternately arranged pillars of first and second conductivity type, featuring implant regions and trench portions filled with semiconductor material, which allows for improved charge balance and breakdown voltage distribution through a combination of epitaxial layers and trench filling processes, enabling better control over electric field concentration and avalanche breakdown.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If IGBT is used for applications greater than 400 volts, then on-resistance is reduced, but switching speed decreases

Engineering Contradiction:

Improveon-resistanceVSAvoidswitching speed

Core Design Contradiction:

StrengthVSSpeed

Solution Approach 1:

The drift region is segmented into multiple alternating n-type and p-type pillars arranged in a superjunction structure. This segmentation allows the electric field to be distributed across multiple junctions, reducing the on-resistance by enabling lower doping concentrations while maintaining high breakdown voltage capability, thus achieving low on-resistance without the severe switching speed penalty of conventional IGBTs

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the device have different doping concentrations and structures - the n-type and p-type pillars have optimized local properties. The alternating pillar structure creates localized charge balance regions that improve electric field distribution, allowing simultaneous optimization of on-resistance and switching characteristics in different parts of the device

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 approach enhances the power device's performance by reducing on-resistance and improving switching speed, allowing for more stable breakdown characteristics and uniformly distributed current flow during UIS events, while maintaining efficient voltage handling.

Implementation Method 1

allows for improved charge balance and breakdown voltage distribution through a combination of epitaxial layers and trench filling processes, enabling better control over electric field concentration and avalanche breakdown

Methodology Applied

Scientific EffectElectric Field: Electric Field

Implementation Method 2

enabling better control over electric field concentration and avalanche breakdown

Methodology Applied

Scientific EffectAvalanche Breakdown: Avalanche Breakdown

Data Source

PatentEP2702611B1Superjunction structures for power devices and methods of manufacture

Publication Date: 2020.05.27 FAIRCHILD SEMICON CORP

Figure 1A~1B
Figure 1C~2
Figure 3

AI summary

A power device includes a semiconductor region which in turn includes a plurality of alternately arranged pillars of first and second conductivity type. Each of the plurality of pillars of second conductivity type further includes a plurality of implant regions of the second conductivity type arranged on top of one another along the depth of pillars of second conductivity type, and a trench portion filled with semiconductor material of the second conductivity type directly above the plurality of implant regions of second conductivity type.