SiC MOSFET Cell Structure With Integrated Schottky Side Trenches
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Solution Overview
Problem
Traditional silicon carbide MOSFET devices face issues with parasitic body PiN diode turn-on, increased packaging cost, and stray inductance due to separate SBD usage, leading to decreased electrical performance and reliability.
Innovation Solution
Integrate a Schottky barrier diode (SBD) within the cellular structure of the silicon carbide MOSFET device, sharing the chip area with the MOSFET, and incorporate a side trench and enhancement region to reduce parasitic effects and optimize area ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate Schottky barrier diode (SBD) is used in anti-parallel manner with MOSFET device, then the parasitic body PiN diode turn-on is suppressed, but the packaging cost increases and stray inductance increases
Solution Approach 1:
The patent combines the MOSFET and SBD into a single integrated device structure where the SBD is formed within the same drift layer and shares common regions with the MOSFET. This merging eliminates the need for separate anti-parallel SBD packaging, reducing packaging cost and stray inductance while maintaining the suppression of parasitic body PiN diode turn-on through the integrated Schottky contact configuration.
Solution Approach 2:
The integrated cellular structure serves multiple functions simultaneously: the MOSFET provides switching capability, the integrated SBD provides freewheeling diode function and suppresses parasitic PiN diode turn-on, and both share common drift layer and substrate regions. This multi-functionality within a single device structure reduces overall system complexity and packaging requirements.
2Reliability
If chip area is increased to accommodate both MOSFET and separate SBD, then the electrical performance is maintained, but the power density decreases
Solution Approach 1:
The MOSFET and SBD are merged into a single integrated cellular structure that shares the drift layer, substrate, and portions of the gate structure. This merging allows both devices to coexist within a smaller chip area compared to separate devices, thereby maintaining electrical performance while increasing power density through more efficient area utilization.
Solution Approach 2:
The SBD structure is nested within the MOSFET cellular structure by sharing the drift layer and substrate regions. The Schottky contact for the SBD is formed in conjunction with the MOSFET gate structure, creating a nested configuration where one device structure is embedded within another, reducing the total area required while maintaining both device functions.
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
Improves chip area utilization, enhances power density, reduces packaging cost, and mitigates bipolar degradation, while maintaining reliability and reducing on-state resistance.
Implementation Method 1
a Schottky metal layer, which is provided in the side trench and forms Schottky contact with the drift layer below the side trench
Implementation Method 2
a source metal layer, which is located above the source region and forms ohmic contact with the source region
Data Source
AI summary
Disclosed is a cellular structure of a silicon carbide MOSFET device, and a silicon carbide MOSFET device. The cellular structure comprises: second conductive well regions located on two sides of the cellular structure and arranged within the surface of a drift layer, first conductive source regions located within the surfaces of the well regions, and a gate structure located at the center of the cellular structure and in contact with the source regions, the well regions, and the drift layer. The cellular structure further comprises a source metal layer located above the source regions and forming ohmic contact with the source regions; on two sides of the cellular structure, side trenches are formed downwardly on regions of the drift layer that are not covered by the well regions; Schottky metal layers forming Schottky contact with the drift layer below the side trenches are arranged in the side trenches.