SiC Trench MOSFET Split-Gate Schottky Structure for Lower VF
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Solution Overview
Problem
Conventional Schottky diodes in semiconductor devices have a high forward voltage drop (VF) that needs to be reduced to improve the switching characteristics of semiconductor devices, particularly in trench gate MOSFETs used in power switches.
Innovation Solution
A semiconductor device with a shielded gate trench metal-oxide-semiconductor field-effect transistor (SGT MOSFET) integrated with a trench MOS barrier Schottky diode region, featuring a split-gate structure, includes a silicon carbide substrate, an epitaxial layer, electrodes, and a source metal layer, which reduces the on-resistance and forward voltage drop by optimizing the conductive structures and dielectric layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional Schottky diode structure is used, then device integration is achieved, but forward voltage drop is high
Solution Approach 1:
The gate structure is segmented into two separate gates (first gate and second gate) positioned on opposite sidewalls of the trench, allowing independent control of different device regions. This segmentation enables optimization of the Schottky diode region to reduce forward voltage drop while maintaining MOSFET switching characteristics
Solution Approach 2:
Different regions of the device are given different doping concentrations and structural characteristics. The Schottky diode region has optimized local properties (doping concentration, gate positioning) to reduce forward voltage drop, while other regions maintain characteristics for proper MOSFET operation
2Productivity
If functional density is increased, then integration capability is improved, but device complexity increases
Solution Approach 1:
The Schottky diode and MOSFET are merged into a single integrated structure sharing common elements (substrate, epitaxial layer, trench structure). This combining achieves high functional density while managing complexity through shared fabrication processes and common structural foundations
Solution Approach 2:
The trench structure serves multiple functions: it provides the gate structure for the MOSFET, defines the Schottky diode region, and enables both switching and rectification functions within a single device footprint, reducing overall device complexity
3Reliability
If gate-to-drain capacitance is reduced, then switching characteristics are improved, but device design complexity increases
Solution Approach 1:
The gate-to-drain capacitance is reduced by extracting or minimizing the overlapping region between the gate and drain electrodes. The separated gate structure on sidewalls reduces parasitic capacitance compared to conventional planar gates, improving switching characteristics without requiring complex additional components
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 integrated structure enhances the switching characteristics and power conversion efficiency of the semiconductor device by reducing gate-to-drain capacitance and feedback capacitance, thereby improving reliability and reducing power losses.
Implementation Method 1
growing an epitaxial layer on a top surface of the silicon carbide substrate
Data Source
AI summary
A semiconductor device and a method for forming the same are provided. The semiconductor device includes a silicon carbide substrate, an epitaxial layer, a first electrode, a separated conductive structure and a source metal layer. The epitaxial layer is disposed on a top surface of the silicon carbide substrate. The first electrode is disposed in the epitaxial layer in the first region of the silicon carbide substrate and extends in a first direction. The separated conductive structure is disposed in the epitaxial layer in the first region. The first conductive feature and the second conductive feature of the separated conductive structure are located on opposite sidewalls of the first electrode. The source metal layer is disposed on the epitaxial layer in the first region. The source metal layer covers and is electrically connected to the first conductive feature, the second conductive feature and the first electrode.