SiC Semiconductor Device With Breakdown Voltage Holding Region
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Solution Overview
Problem
SiC power devices face issues with increased ON resistance and high forward voltage loss due to crystal defect expansion and parasitic diode conduction, which can lead to dielectric breakdown in the gate insulating film.
Innovation Solution
A semiconductor device with a wide band gap semiconductor structure featuring a source trench, gate insulating film, and breakdown voltage holding regions to direct reflux current through a Schottky or hetero junction, reducing carrier recombination and electric field concentration on the gate insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-n body diode is formed by p-n junction between p-type channel region and n-type drain region, then reflux current can be rectified, but carrier recombination causes crystal defect expansion and ON resistance increase
Solution Approach 1:
The patent changes the junction type from p-n junction to Schottky junction by forming a metal layer on the n-type drain region. This parameter change eliminates carrier recombination while maintaining reflux current rectification capability, thereby preventing ON resistance increase.
2Manufacturing precision
If Schottky junction is formed to reduce carrier recombination, then ON resistance can be suppressed, but electric field concentrates on gate insulating film causing dielectric breakdown
Solution Approach 1:
The patent introduces an intermediate layer between the metal layer and n-type drain region to distribute the electric field. This intermediary structure prevents electric field concentration on the gate insulating film while maintaining the low ON resistance benefit of the Schottky junction.
3Ease of manufacture
If metal layer is formed directly on n-type drain region, then Schottky junction can be formed, but electric field concentration occurs on gate insulating film
Solution Approach 1:
The patent uses a composite structure with multiple layers (metal layer + intermediate layer) instead of a single metal layer. This composite material approach enables Schottky junction formation while distributing electric field stress, preventing gate insulating film breakdown.
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 suppresses ON resistance increase, enhances withstanding voltage, and prevents dielectric breakdown, thereby improving the reliability and performance of SiC power devices.
Implementation Method 1
form a Schottky junction between a source electrode and the n-type drain region exposed in the trench
Implementation Method 2
forming, by junction with the drain region, a junction barrier lower than a diffusion potential of a body diode
Implementation Method 3
causing a dielectric breakdown of the gate insulating film
Implementation Method 4
rectification of a parasitic diode (a body diode) by p-n junction between a p-type channel region and an n-type drain region
Implementation Method 5
a majority carrier electron sometimes recombines with a positive hole, which has transferred from the p-type channel region, in the n-type drain region. Energy generated at the time of recombination
Data Source
AI summary
A semiconductor device of the present invention is a semiconductor device having a semiconductor layer comprising a wide band gap semiconductor, wherein the semiconductor layer includes: a first conductivity-type source region, a second conductivity-type channel region and a first conductivity-type drain region, which are formed in this order from the surface side of the semiconductor layer; a source trench lying from the surface of the semiconductor layer through the source region and the channel region to the drain region; a gate insulating film formed so as to contact the channel region; a gate electrode facing the channel region with the gate insulating film interposed therebetween; and a first breakdown voltage holding region of a second conductivity type formed selectively on the side face or the bottom face of the source trench, and the semiconductor device includes a barrier formation layer, which is joined with the drain region in the source trench, for forming, by junction with the drain region, a junction barrier lower than a diffusion potential of a body diode formed by p-n junction between the channel region and the drain region.