Semiconductor Device Band Gap Engineering for Avalanche Protection

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Solution Overview

Problem

Power semiconductor elements, such as MOSFETs and IGBTs, are prone to breakage due to avalanche breakdown phenomena, particularly in the peripheral regions, where local current concentration exceeds the avalanche resistance, leading to potential device failure. To enhance reliability, it is crucial to prevent avalanche breakdown in peripheral regions before it occurs in cell regions.

Innovation Solution

The solution involves forming a lower band gap region in the cell region and a higher band gap region in the peripheral region, with the lower band gap region being deeper than half the depth of the p column region and the higher band gap region being shallower, to direct avalanche breakdown to occur in the cell region where current concentration is lower, thereby preventing peripheral region failure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the avalanche breakdown voltage of the peripheral region is made higher than the cell region to prevent breakage, then reliability is improved, but device complexity increases due to the need for different band gap regions

Engineering Contradiction:

Improveavalanche resistanceVSAvoiddevice structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by creating different band gap regions at specific locations within the semiconductor device. A first band gap region with a lower band gap is formed in the cell region, while a second band gap region with a higher band gap is formed in the peripheral region. This spatial differentiation of material properties ensures that avalanche breakdown occurs preferentially in the cell region with lower breakdown voltage, protecting the peripheral region from damage while maintaining overall device reliability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent utilizes parameter changes by varying the band gap energy of the semiconductor material in different regions. By controlling the band gap parameter - lower in the cell region and higher in the peripheral region - the invention achieves different avalanche breakdown voltages in these regions. This parameter differentiation allows the cell region to undergo controlled avalanche breakdown while the peripheral region remains protected, resolving the contradiction between reliability and complexity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If avalanche breakdown is allowed in the cell region to protect peripheral regions, then peripheral region reliability is improved, but the risk of excessive current flow increases

Engineering Contradiction:

Improveperipheral region protectionVSAvoidcurrent concentration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent converts the potentially harmful avalanche breakdown phenomenon into a beneficial protective mechanism. By designing the cell region with a lower band gap, the invention intentionally allows avalanche breakdown to occur in this region, which acts as a sacrificial protection mechanism. The controlled breakdown in the cell region prevents more severe damage in the peripheral region, thus converting a harmful electrical phenomenon into a useful protective function.

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 configuration effectively suppresses avalanche breakdown in peripheral regions, reducing the risk of device breakage by ensuring avalanche breakdown occurs in the cell region with lower current concentration, thus enhancing the reliability of power semiconductor devices.

Implementation Method 1

When the voltage exceeds the avalanche breakdown voltage, an avalanche breakdown phenomenon occurs in the power semiconductor element, so that an avalanche current flows therethrough

Methodology Applied

Scientific EffectAvalanche breakdown: Avalanche Breakdown

Data Source

PatentUS9520318B2Semiconductor device

Publication Date: 2016.12.13 RENESAS ELECTRONICS CORP

AI summary

A method for manufacturing a semiconductor device including a cell region and a peripheral region formed outside the cell region, comprising the steps of (a) providing a semiconductor substrate including a first epitaxial layer of a first conductivity type formed over a main surface thereof, (b) doping a lower band gap impurity for making the band gap smaller than the band gap of the first epitaxial layer before doping into the first epitaxial layer in the cell region, and thereby forming a lower band gap region, (c) after the step (b), forming a plurality of first column regions of a second conductivity type which is the opposite conductivity type to the first conductivity type in such a manner as to be separated from one another in the first epitaxial layer extending from the cell region to the peripheral region, and (d) after the step (c), forming a second epitaxial layer.