SiC MISFET Gate Layout for Dielectric Breakdown Suppression
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices experience dielectric breakdown of the gate insulating film during high-speed switching operations, which is not fully suppressed.
Innovation Solution
The silicon carbide semiconductor device design includes a silicon carbide substrate with specific conductivity type layers, discrete body regions, and a unique arrangement of gate electrodes and contacts that prevent overlap with the gate pad, reducing the potential difference across the gate insulating film and minimizing displacement current impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gate electrode and gate pad arrangement is used, then device structure is simple, but dielectric breakdown of gate insulating film occurs during high-speed switching
Solution Approach 1:
The patent applies dimensional separation by arranging gate electrodes and gate pad in different planar regions so they do not overlap when viewed from the surface. This spatial reconfiguration in the horizontal plane eliminates the harmful vertical alignment that causes dielectric breakdown during high-speed switching, while maintaining overall device functionality.
Solution Approach 2:
The patent extracts the harmful overlap configuration between gate electrodes and gate pad from the device structure. By removing this specific geometric relationship, the source of displacement current-induced breakdown is eliminated, allowing the device to operate reliably at high switching speeds without requiring complex additional protective structures.
2Ease of manufacture
If gate electrodes overlap with gate pad, then manufacturing is simpler, but displacement current causes dielectric breakdown
Solution Approach 1:
The patent resolves the manufacturing complexity by using planar separation instead of vertical stacking. The gate electrodes and gate pad are positioned in different horizontal zones, which eliminates displacement current effects while maintaining straightforward fabrication processes that do not require precise vertical alignment.
Solution Approach 2:
The patent converts the potential harm of close proximity between gate electrodes and gate pad into a benefit by using their spatial separation to define distinct functional zones. This arrangement naturally guides current flow paths and reduces electromagnetic interference while simplifying the manufacturing process through clear regional differentiation.
3Productivity
If high-speed switching is implemented, then device performance improves, but dielectric breakdown risk increases
Solution Approach 1:
The patent applies preliminary anti-action by pre-configuring the gate electrode and gate pad positions to prevent overlap before high-speed switching operations begin. This proactive spatial arrangement eliminates the conditions that would generate harmful displacement currents during rapid switching, allowing high-performance operation without compromising gate insulating film stability.
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 design effectively suppresses dielectric breakdown of the gate insulating film during high-speed switching, ensuring safe and reliable operation by reducing the potential difference and contact resistance, thereby preventing device failure.
Implementation Method 1
The silicon carbide semiconductor substrate is of the first conductivity type and includes a first conductivity type drift layer. A plurality of the first body regions are of the second conductivity type and are formed in a discrete manner on a surface of the drift layer.
Implementation Method 2
The gate insulating film is positioned above the plurality of first body regions, the source regions, and the second body region. This design effectively suppresses dielectric breakdown of the gate insulating film during high-speed switching.
Implementation Method 3
It has been known that, when a silicon carbide power semiconductor device is used as a switching element, PN-junction capacitance may induce a displacement current, leading to breakdown of the gate insulating film of a field-effect transistor.
Data Source
AI summary
The silicon carbide semiconductor device includes a plurality of unit cells each having an MISFET structure and provided on a silicon carbide semiconductor substrate. A gate upper electrode disposed adjacent to the plurality of unit cells includes a gate pad and gate global wires. When viewed in plan, gate electrodes do not overlap with the gate pad.