Schottky Electrode for Power Diode Reverse Recovery

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Solution Overview

Problem

Power diode elements in semiconductor devices face breakdown due to high reverse recovery current and electric field density, particularly at the anode electrode's peripheral edge and outer curvature portions, which compromises their reverse-recovery immunity.

Innovation Solution

Incorporating a Schottky electrode connected to the anode electrode's extension portion and a second conductivity-type extraction region deeper than the anode region, along with field limiting rings, to reduce current concentration and electric field density, thereby enhancing reverse-recovery immunity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a power diode element is designed to handle high reverse recovery current, then the reverse-recovery immunity is improved, but current concentration occurs at the peripheral edge portion of the anode electrode and outer curvature portion, leading to breakdown

Engineering Contradiction:

Improvereverse-recovery immunityVSAvoidcurrent concentration and electric field density

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating a p-type annular diffusion region with different doping characteristics than the main anode region. This annular region is positioned specifically at the peripheral edge portion where current concentration occurs, providing localized electric field relaxation without affecting the overall diode performance. The different doping concentration and depth in this specific location address the harmful electric field density precisely where it causes breakdown.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces a depth dimension by creating an annular diffusion region that extends deeper than the main anode region. This vertical dimensionality change allows the electric field to be relaxed at the outer curvature portion through the deeper p-type region, providing a three-dimensional solution to the two-dimensional current concentration problem at the peripheral edge.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Power

If the anode electrode is designed with extended peripheral contact, then the current handling capability is improved, but the electric field density increases at the outer curvature portion causing breakdown

Engineering Contradiction:

Improvecurrent handling capabilityVSAvoidelectric field density at outer curvature

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The p-type annular diffusion region provides localized modification at the peripheral edge portion where the anode electrode contacts. This annular region has different doping concentration and extends to different depth, creating a localized zone that relaxes the electric field density specifically at the outer curvature portion where the harmful effects occur, while maintaining the extended peripheral contact for current handling.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements beforehand cushioning by pre-positioning the p-type annular diffusion region with higher doping concentration at the peripheral edge portion before reverse recovery occurs. This pre-configured structure acts as a cushion that relaxes the electric field density in advance, preventing breakdown caused by high electric field density at the outer curvature portion during reverse recovery events.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

The solution effectively decreases hole current density and impact ionization rates, improving the diode element's reverse-recovery immunity and minimizing chip size by distributing carrier extraction and reducing current concentration at critical areas.

Implementation Method 1

a Schottky electrode Schottky-contacted to a peripheral portion of the anode region

Methodology Applied

Scientific EffectSchottky contact:

Data Source

PatentUS10229970B2Semiconductor device having schottky electrode connected to anode region

Publication Date: 2019.03.12 FUJI ELECTRIC CO LTD

AI summary

For enhancing a reverse-recovery immunity of a diode element, a semiconductor device includes a first conductivity-type drift layer, a second conductivity-type anode region provided in an upper portion of the drift layer, an insulating film provided on the drift layer, an anode electrode having an ohmic contact portion ohmically contacted to the anode region through a contact hole penetrating the insulating film, and a Schottky electrode Schottky-contacted to a peripheral portion of the anode region.