SiC MOSFET Transition-Zone Doping for Body Diode Conduction
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Solution Overview
Problem
Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) face challenges in increasing the forward current of their parasitic body diode, which results in higher power loss and reduced reliability due to the high forward voltage drop of the P-N diode, and modifying the device to address this either increases complexity and cost or decreases channel conductance.
Innovation Solution
The semiconductor device includes a semiconductor substrate with an epitaxial layer, a cell zone with unit cells, a transition zone with a doped region, and a source electrode unit, where the doped region is connected to the well contact region of the unit cells, allowing for increased current flow without increasing the overall device area, and a method for manufacturing this device involving ion implantation to form well and source regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the surface area of the P+ region in a unit cell is increased to increase the forward current of the body diode, then the forward current capability is improved, but the channel conductance and current density of the SiC MOSFET decrease
Solution Approach 1:
The patent divides the source electrode into two separate portions: a first source electrode portion connected to the well contact region and a second source electrode portion connected to the doped region of the transition zone. This segmentation allows independent optimization of the body diode current path and the channel conductance path, resolving the contradiction between increasing body diode forward current and maintaining channel conductance.
2Loss of energy
If a schottky diode is used to replace the P-N diode to decrease power loss, then the power loss of the body diode is reduced, but the fabrication process complexity and device cost increase
Solution Approach 1:
The patent utilizes the parasitic body diode structure that naturally exists in the SiC MOSFET device itself, rather than adding a separate schottky diode component. The doped region in the transition zone serves dual purposes: it provides a low-impedance path for the body diode current and integrates seamlessly with the existing MOSFET structure, eliminating the need for additional fabrication steps and reducing overall device complexity.
3Power
If the doped region in the transition zone is directly connected to the well contact region to increase current flow, then the forward current capability is improved, but the device area increases
Solution Approach 1:
The doped region is positioned within the transition zone that already exists between the cell zone and the drift region, effectively utilizing the existing device structure space. The second source electrode portion connects to this doped region, creating a nested configuration that increases current flow capability without requiring additional lateral device area.
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 enhances the current flow capability of the body diode, reduces power loss, and improves heat dissipation while maintaining device reliability and reducing fabrication costs.
Implementation Method 1
The doped region of the transition zone has the first conductive type, is disposed in the epitaxial layer opposite to the semiconductor substrate, and is directly connected to the well contact region of at least one of the unit cells
Implementation Method 2
a method for manufacturing this device involving ion implantation to form well and source regions
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, an epitaxial layer disposed on the semiconductor substrate, a cell zone including multiple unit cells disposed in the epitaxial layer opposite to the semiconductor substrate, a transition zone having a doped region and surrounding the cell zone, a source electrode unit disposed on the epitaxial layer opposite to the semiconductor substrate, and multiple gate electrode units. Each unit cell includes a well region, a source region disposed in the well region, and a well contact region extending through the source region to contact the well region. A method for manufacturing the semiconductor device is also disclosed.