SiC Trench Gate Insulation Withstand Voltage
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Solution Overview
Problem
Silicon carbide semiconductor devices with trench gate structures face challenges in achieving high insulation withstand voltage and lifetime due to concavity and convexity formations on the sidewall and bottom of the trench, which are exacerbated by the higher electric field intensity compared to silicon semiconductor devices.
Innovation Solution
The silicon carbide semiconductor device is designed with a trench gate structure where the longitudinal direction of the trench is perpendicular to the offset direction of the substrate, minimizing the formation of concavity and convexity on the sidewall and bottom of the trench, thereby improving the insulation withstand voltage and lifetime of the gate insulation film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a trench gate structure is used to increase channel density, then current carrying capacity is improved, but concavity and convexity form on the sidewall and bottom of the trench causing reduced insulation withstand voltage and shortened lifetime
Solution Approach 1:
The patent changes the geometric parameters of the trench gate structure by introducing a curvature radius R at the bottom corner of the trench. This parameter modification prevents the formation of concavity and convexity while maintaining the trench gate structure's current carrying capacity, thereby resolving the contradiction between productivity and reliability
Solution Approach 2:
The patent introduces asymmetric curvature design at the trench bottom corners with specific radius R, creating an optimized geometry that eliminates stress concentration points. This asymmetric modification prevents electric field concentration while preserving the vertical channel structure needed for high current density
2Strength
If the breakdown electric field intensity is increased ten times for SiC devices, then voltage handling capability is improved, but the gate insulation film experiences higher electric field stress reducing its insulation withstand voltage and lifetime
Solution Approach 1:
The patent modifies the geometric parameters of the trench structure by introducing a curvature radius R at the bottom corners. This parameter change distributes the electric field more uniformly, preventing concentration at sharp corners while maintaining the high voltage handling capability of SiC devices
Solution Approach 2:
The patent preemptively introduces curved transition regions at the trench bottom corners before the high voltage operation begins. This prior geometric modification acts as a cushioning measure that prevents electric field concentration and protects the gate insulation film from premature breakdown under high voltage stress
Data Source
AI summary
A SiC semiconductor device includes: a SiC substrate including a first or second conductive type layer and a first conductive type drift layer and including a principal surface having an offset direction; a trench disposed on the drift layer and having a longitudinal direction; and a gate electrode disposed in the trench via a gate insulation film. A sidewall of the trench provides a channel formation surface. The vertical semiconductor device flows current along with the channel formation surface of the trench according to a gate voltage applied to the gate electrode. The offset direction of the SiC substrate is perpendicular to the longitudinal direction of the trench.