SiC Transistor Body Region Segmentation for Drain-Induced Barrier Lowering

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Solution Overview

Problem

Short-channel effects, specifically drain-induced barrier lowering, occur in silicon carbide devices due to the penetration of the space-charge region into the body region, affecting the threshold voltage and electrical characteristics of transistors.

Innovation Solution

A silicon carbide device design with a body region comprising multiple doping portions, where the first portion acts as a fieldstop to reduce space-charge region penetration, and a method involving implantation of dopants with specific doses and energies to form these portions, ensuring the first portion has a higher net doping concentration and extension to effectively mitigate drain-induced barrier lowering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the transistor size is shrunk to improve integration density, then productivity increases, but short-channel effects worsen due to space-charge region penetration into the body region

Engineering Contradiction:

Improveintegration densityVSAvoidshort-channel effects

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The body region is segmented into multiple portions with different doping concentrations. The first portion has a higher net doping concentration than the second portion, creating distinct zones that collectively suppress space-charge region penetration while maintaining compact dimensions. This segmentation allows the transistor to achieve high integration density without suffering from short-channel effects.

Inventive Principle:

Principle #1Segmentation

2Reliability

If the body region doping concentration is increased to reduce space-charge region penetration, then reliability improves, but manufacturing complexity increases due to multiple doping portions

Engineering Contradiction:

Improvethreshold voltage stabilityVSAvoidbody region structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Different portions of the body region are assigned different doping concentrations according to their specific functional requirements. The first portion, located adjacent to the drift region, has a higher doping concentration to effectively block space-charge region penetration, while the second portion has a lower concentration to maintain proper electrical characteristics. This local quality differentiation achieves reliable threshold voltage control without excessive manufacturing complexity.

Inventive Principle:

Principle #3Local quality

3Reliability

If the first portion extension is increased to improve fieldstop effect, then reliability improves, but device area increases

Engineering Contradiction:

Improvedrain-induced barrier lowering reductionVSAvoidbody region area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The net doping concentration parameter is changed across different portions of the body region. The first portion has a higher net doping concentration that creates a strong fieldstop effect with a relatively small extension, while the second portion has a lower concentration. This parameter change allows effective suppression of drain-induced barrier lowering without significantly increasing the overall device area, enabling high integration density.

Inventive Principle:

Principle #35Parameter changes

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 reduces drain-induced barrier lowering, improves the electrical characteristics of silicon carbide devices by minimizing space-charge region penetration, thereby maintaining a stable threshold voltage and enhancing switching performance.

Implementation Method 1

The first portion acts as a fieldstop to reduce space-charge region penetration

Methodology Applied

Scientific EffectFieldstop effect:

Implementation Method 2

The method comprises implanting first dopants into a silicon carbide substrate with a first implantation dose to form a first portion of a body region

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Data Source

PatentUS11264464B2Silicon carbide devices and methods for forming silicon carbide devices

Publication Date: 2022.03.01 INFINEON TECHNOLOGIES AG

AI summary

A silicon carbide device includes a transistor cell with a front side doping region, a body region, and a drift region. The body region includes a first portion having a first average net doping concentration and a second portion having a second average net doping concentration. The first portion and the second portion have an extension of at least 50 nm in a vertical direction. The first average net doping concentration is at least two times the second average net doping concentration, and the first average net doping concentration is at least 1·1017 cm−3.