SiC Schottky Diode Pillar Segmentation for On-Resistance
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Solution Overview
Problem
Conventional Schottky barrier diodes (SBDs) face increased on-resistance due to a p+ area in the schottky junction, which also reduces breakdown voltage when reverse voltage is applied, as it decreases the contact area with the n-epitaxial layer or n-drift layer and increases resistance.
Innovation Solution
The SBD design includes n-type pillar areas with higher doping concentration within the n-type epitaxial layer and a p-type area extended perpendicular to the pillars, with p+ areas separated from both, and a schottky electrode on the n-type epitaxial and p+ areas, along with an ohmic electrode on the substrate, to reduce on-resistance and maintain breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p+ area is formed in the schottky junction portion to improve leakage current reduction characteristics, then breakdown voltage is improved, but contact area with n-epitaxial layer decreases and on-resistance increases
Solution Approach 1:
The schottky junction area is divided into multiple discrete p+ areas rather than a continuous p+ region. This segmentation allows the diode to maintain adequate contact area between the schottky electrode and n-epitaxial layer while still forming depletion layers at each p+ area for leakage current interception. The multiple separated p+ areas provide sufficient breakdown voltage protection without excessively increasing on-resistance.
Solution Approach 2:
The p+ areas are strategically positioned at specific locations within the schottky junction portion rather than uniformly distributed. This local quality approach concentrates the leakage current interception function at critical points while preserving contact area in other regions, thereby balancing breakdown voltage improvement with on-resistance management.
2Reliability
If p+ areas are increased to improve leakage current reduction, then breakdown voltage is improved, but current path area for forward direction decreases
Solution Approach 1:
The schottky junction is segmented into multiple discrete p+ areas rather than using a large continuous p+ region. This segmentation provides sufficient depletion layer coverage for leakage current interception and breakdown voltage improvement while preserving adequate contact area for forward current flow through the remaining n-epitaxial layer regions.
Solution Approach 2:
Instead of covering the entire schottky junction with p+ areas, only partial regions are doped with p+ ions. This partial action is sufficient to create the necessary depletion layers for leakage current interception while maintaining adequate current path area for forward direction conduction.
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 reduces on-resistance when forward voltage is applied and prevents breakdown voltage reduction when reverse voltage is applied by optimizing current flow and electric field distribution.
Implementation Method 1
n-type pillar areas with higher doping concentration within the n-type epitaxial layer... reduces on-resistance when forward voltage is applied
Implementation Method 2
by applying a structure of a junction barrier schottky (JBS) in which a p+ area is formed to a lower end portion of a schottky junction portion, and by overlapping of a PN diode depletion layer that is diffused when an inverse voltage is applied, a leakage current is intercepted and a breakdown voltage is improved
Data Source
AI summary
A schottky barrier diode includes: an n− type epitaxial layer that is disposed at a first surface of an n+ type silicon carbide substrate; a plurality of n type pillar areas that are disposed at the inside of the n− type epitaxial layer and that are disposed at a first portion of the first surface of the n+ type silicon carbide substrate; a p type area that is disposed at the inside of the n− type epitaxial layer and that is extended in a direction perpendicular to the n type pillar areas; a plurality of p+ areas in which the n− type epitaxial layer is disposed at a surface thereof and that are separated from the n type pillar areas and the p type area; a schottky electrode that is disposed on the n− type epitaxial layer and the p+ areas; and an ohmic electrode that is disposed at a second surface of the n+ type silicon carbide substrate.