SiC Schottky Diode Pad Insulation for Field Concentration

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Solution Overview

Problem

Silicon carbide Schottky barrier diodes (SBDs) face electric field concentration issues near the outer peripheral end of the Schottky electrode during high-frequency switching operations, leading to potential faults and withstand voltage degradation due to sharpened etching residues and displacement currents.

Innovation Solution

A silicon carbide semiconductor device design featuring a drift layer, annular guard ring region, field insulating film, Schottky electrode covering the guard ring, and a surface electrode pad that contacts the insulating film over the Schottky electrode's outer peripheral end, effectively covering the etching residue and preventing electric field concentration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the Schottky electrode is extended over the outer peripheral end of the guard ring region to extend the depletion layer, then the voltage blocking ability is improved, but electric field concentration occurs at the outer peripheral end during high-frequency switching operations

Engineering Contradiction:

Improvevoltage blocking abilityVSAvoidreliability during high-frequency switching

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The Schottky electrode structure is segmented into two distinct parts: an inner region that extends over the guard ring to provide voltage blocking capability, and an outer region that is separated from the guard ring by the insulating film to prevent electric field concentration. This segmentation allows each part to fulfill its specific function without interfering with the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An insulating film is introduced as an intermediary element between the outer peripheral end of the Schottky electrode and the guard ring region. This insulating film acts as a mediator that electrically isolates the two regions, preventing the formation of high electric fields at their interface during high-frequency switching operations while allowing the inner Schottky electrode to maintain voltage blocking capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If the Schottky electrode is formed by etching with an overlay structure, then the depletion layer extends easily in the n-type semiconductor layer, but etching residues with sharpened extreme ends occur that concentrate electric fields

Engineering Contradiction:

Improveease of forming depletion layerVSAvoidelectric field concentration at etching residues

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The harmful etching residue portion is extracted or removed from the functional Schottky electrode structure by introducing the insulating film. The insulating film is placed between the outer peripheral end of the Schottky electrode and the guard ring, effectively isolating and removing the harmful effect of the sharpened etching residue extreme end from the electric field path.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The insulating film converts the potentially harmful etching residue structure into a beneficial configuration. By placing the insulating film between the Schottky electrode and guard ring, the previously harmful sharpened extreme end of the etching residue is now electrically isolated and cannot concentrate electric fields, while the inner Schottky electrode structure continues to provide the desired depletion layer extension.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 design enhances the reliability of silicon carbide semiconductor devices during high-frequency switching operations by preventing electric field concentration, thereby improving withstand voltage and reducing the risk of faults.

Implementation Method 1

a Schottky electrode covering the guard ring region and the drift layer exposed inside the guard ring region

Methodology Applied

Scientific EffectSchottky junction:

Implementation Method 2

an overlay structure in which a Schottky electrode is extended over the outer peripheral end of a guard ring region is provided in order to extend a depletion layer produced around a PN junction

Methodology Applied

Scientific EffectDepletion layer:

Implementation Method 3

a field insulating film formed on the one surface of the drift layer and surrounding the guard ring region

Methodology Applied

Scientific EffectElectrical insulation:

Implementation Method 4

an outer peripheral end of the surface electrode pad comes into contact with the field insulating film over the outer peripheral end of the Schottky electrode

Methodology Applied

Scientific EffectElectrical contact:

Data Source

PatentUS9184307B2Silicon carbide semiconductor device

Publication Date: 2015.11.10 MITSUBISHI ELECTRIC CORP

AI summary

A silicon carbide semiconductor device includes: a drift layer of the a first conduction type; a guard ring region of a second conduction type formed in annular form in a portion of one surface of the drift layer; a field insulating film formed on the one surface of the drift layer and surrounding the guard ring region; a Schottky electrode covering the guard ring region and the drift layer exposed inside the guard ring region and having an outer peripheral end existing on the field insulating film; and a surface electrode pad on the Schottky electrode, wherein an outer peripheral end of the surface electrode pad comes into contact with the field insulating film over the outer peripheral end of the Schottky electrode.