SiC Drift Region Carrier Tuning via Particle Beam Defects

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Solution Overview

Problem

Conventional silicon carbide semiconductor devices face challenges in controlling the variation of majority carrier concentration in the n−-type drift region, leading to inconsistencies in ON resistance and breakdown voltage, especially under high temperature conditions.

Innovation Solution

The silicon carbide semiconductor device incorporates a method where a particle beam is irradiated to introduce point defects in the n−-type drift region, adjusting the effective majority carrier concentration to be lower than the impurity concentration, thereby reducing variation and optimizing device performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If epitaxial growth is performed at high temperature (about 1600 degrees C) to form the n−-type drift region, then the drift region can be formed with appropriate doping, but the majority carrier concentration varies significantly (±15% from target value between chips)

Engineering Contradiction:

Improvemajority carrier concentration controlVSAvoiddevice performance consistency

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies parameter changes by introducing point defects through particle beam irradiation to modify the electrical characteristics of the drift region. The irradiation dose is controlled to create a specific density of point defects that compensate for the high-temperature epitaxial growth variations, thereby adjusting the majority carrier concentration to match target values across different chips.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the purely thermal process (epitaxial growth at 1600°C) with a combined approach involving particle beam irradiation. This substitution introduces a new mechanism (radiation-induced point defects) to control carrier concentration, complementing the thermal growth process and achieving better precision than temperature control alone.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of manufacture

If high temperature epitaxial growth is used to form the drift region, then the doping process can be completed, but the ON resistance and breakdown voltage show significant variation

Engineering Contradiction:

Improvedrift region formationVSAvoidON resistance and breakdown voltage control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent changes the physical state of the drift region by introducing point defects through particle beam irradiation. This creates a new parameter (defect density) that can be independently controlled to adjust electrical characteristics, thereby achieving precise control of ON resistance and breakdown voltage despite variations in the epitaxial growth process.

Inventive Principle:

Principle #35Parameter changes

3Strength

If the majority carrier concentration is reduced to optimize breakdown voltage, then voltage withstanding capability improves, but ON resistance increases

Engineering Contradiction:

Improvebreakdown voltageVSAvoidON resistance

Core Design Contradiction:

StrengthVSPower

Solution Approach 1:

The patent applies local quality by creating point defects specifically in the drift region through particle beam irradiation. These localized defects provide compensation that allows independent optimization of breakdown voltage and ON resistance, decoupling the trade-off that would otherwise require uniform changes in doping concentration across the entire drift region.

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 effectively reduces the variation of the effective majority carrier concentration in the n−-type drift region, stabilizing the ON resistance and breakdown voltage, and enhancing the device's performance under high temperature conditions.

Implementation Method 1

a particle beam is irradiated to introduce point defects in the n−-type drift region, adjusting the effective majority carrier concentration to be lower than the impurity concentration

Methodology Applied

Scientific EffectParticle beam irradiation: Ion Beam

Data Source

PatentUS12224320B2Silicon carbide semiconductor device and method of manufacturing silicon carbide semiconductor device

Publication Date: 2025.02.11 FUJI ELECTRIC CO LTD

AI summary

At any timing after formation of gate electrodes, particle beam irradiation is performed to a semiconductor wafer having an n−-type drift region constituted by an n−-type epitaxial layer and having an n-type impurity concentration that is higher than a target majority carrier concentration (design value) of the n−-type drift region. Point defects of a defect density corresponding to an irradiation dose of the particle beam are generated in the n−-type drift region by the particle beam irradiation, whereby an effective majority carrier concentration of the n−-type drift region is adjusted and reduced with respect to the n-type impurity concentration of the n−-type drift region, to approach the design value. After formation of the n−-type epitaxial layer, the n-type impurity concentration of the n−-type drift region may be measured, or the n−-type epitaxial layer may be formed to have an n-type impurity concentration higher than the design value.