MPS Diode Structure With Floating Doped Regions for Low Leakage
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Solution Overview
Problem
Wide bandgap semiconductor diodes, such as silicon carbide (SiC) JBS diodes, suffer from reverse current leakage due to large Schottky contact areas, which deteriorates forward voltage (VF) characteristics.
Innovation Solution
A merged PiN Schottky (MPS) diode design with floating doped regions and a Schottky metal layer, where the first portions of the doped regions are electrically floating and the second portions are connected to the top metal, reducing current leakage and improving forward voltage characteristics by preventing depletion regions and increasing Schottky contact area without increasing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Schottky contact area is increased to improve device performance, then the rectifying capability is enhanced, but reverse current leakage increases and forward voltage characteristics deteriorate
Solution Approach 1:
The doped regions are divided into first portions (extending to the Schottky metal layer interface) and second portions (embedded in the drift layer). This segmentation allows different functional zones: the first portions provide rectifying action at the interface while the second portions provide conductivity modulation without causing leakage, thus resolving the contradiction between rectifying capability and reverse current leakage.
Solution Approach 2:
Different regions of the doped structures are given different electrical properties: the first portions are configured to form ohmic contact with the Schottky metal layer for local rectifying action, while the second portions are configured to be electrically isolated to provide localized conductivity modulation. This local differentiation allows the Schottky contact area to be increased without proportionally increasing leakage paths.
2Reliability
If the Schottky contact area is increased to improve device performance, then the rectifying capability is enhanced, but forward voltage characteristics deteriorate
Solution Approach 1:
By segmenting the doped regions into first and second portions with different electrical connections, the device achieves distributed rectifying action across the Schottky interface (improving rectifying capability) while maintaining localized conductivity modulation zones that reduce overall forward voltage drop, thus resolving the contradiction between rectifying capability and forward voltage characteristics.
3Loss of energy
If doped regions are fully connected to metal to provide conductivity modulation, then forward conduction is improved, but reverse current leakage increases
Solution Approach 1:
The doped regions are segmented into first portions connected to the Schottky metal layer interface and second portions embedded and electrically isolated in the drift layer. The first portions provide rectifying action without causing leakage, while the second portions provide conductivity modulation for improved forward conduction. This segmentation resolves the contradiction by separating the leakage-causing connection from the beneficial modulation function.
Solution Approach 2:
Different electrical connection qualities are applied to different portions of the doped regions: the first portions have local ohmic connection to the Schottky interface for rectifying action, while the second portions have local electrical isolation to provide conductivity modulation without creating leakage paths. This local quality differentiation resolves the contradiction between forward conduction improvement and reverse leakage prevention.
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 MPS diode effectively reduces current leakage and enhances forward voltage characteristics by utilizing floating doped regions to manage electric fields and maintain low Schottky barrier heights, even with increased Schottky contact area.
Implementation Method 1
a Schottky barrier diode (SBD) having a carrier potential barrier of a difference in work function between a semiconductor layer and metal
Implementation Method 2
a carrier potential barrier of a difference in work function between a semiconductor layer and metal
Implementation Method 3
the first portions are electrically floating... reducing current leakage and improving forward voltage characteristics by preventing depletion regions
Implementation Method 4
a minority carrier is injected to decrease a resistance by conductivity modulation when a voltage exceeding a built-in potential (Vbi) between the doping region and the semiconductor layer is applied
Data Source
AI summary
A merged PiN Schottky (MPS) diode includes a substrate, a first epitaxial layer of a first conductivity type, doped regions of a second conductivity type, a second epitaxial layer of the first conductivity type, and a Schottky metal layer. The first epitaxial layer is disposed on the first surface of the substrate. The doped regions are disposed in a surface of the first epitaxial layer, wherein the doped regions consist of first portions and second portions, the first portions are electrically floating, and the second portions are electrically connected to a top metal. The second epitaxial layer is disposed on the surface of the first epitaxial layer, wherein trenches are formed in the second epitaxial layer to expose the second portions of the doped regions. The Schottky metal layer is conformally deposited on the second epitaxial layer and the exposed second portions of the doped regions.