SiC Trench Gate Shielding Region for Lower Gate-Drain Capacitance
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Solution Overview
Problem
Silicon carbide devices face limitations in their range of applications due to challenges with LC oscillations when switching heavy inductive loads and high on-state resistance, which affects their performance in high-voltage applications.
Innovation Solution
A silicon carbide device with a stripe-shaped trench gate structure and a shielding region of a second conductivity type that extends across at least 20% of the gate length, reducing gate-to-drain capacitance and improving switching behavior by increasing the contact area and reducing ohmic contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If silicon carbide devices are used for high-voltage applications, then the dielectric breakdown field strength is improved, but the on-state resistance becomes significantly lower which limits the range of applications
Solution Approach 1:
The patent introduces a shielding region with a different conductivity type (opposite to the drift region) that is selectively positioned at specific locations (first bottom edge of gate structure) where it is most needed. This local modification allows the device to maintain high breakdown strength in critical areas while managing on-state resistance and reducing oscillations, thereby expanding application versatility without sacrificing voltage blocking capability.
2Power
If silicon carbide devices switch heavy inductive loads, then the switching capability is improved, but LC oscillations are triggered which reduces reliability
Solution Approach 1:
The shielding region acts as an intermediary element between the gate structure and the drift region. By introducing this intermediate region with opposite conductivity type, the patent effectively decouples the direct interaction that causes LC oscillations, allowing heavy inductive load switching while suppressing oscillations and improving reliability.
3Reliability
If the gate structure contact area is increased, then the ohmic contact resistance is reduced, but the device complexity increases
Solution Approach 1:
Rather than uniformly increasing the contact area of the entire gate structure, the patent segments the contact region by introducing a shielding region at a specific location (first bottom edge). This segmented approach increases the effective contact area for ohmic connection where needed, while keeping the rest of the gate structure simple and manageable.
Data Source
AI summary
A method of producing a silicon carbide (SiC) device includes: forming a stripe-shaped trench gate structure that extends from a first surface of a SiC body into the SiC body, the gate structure having a gate length along a lateral first direction, a bottom surface and a first gate sidewall of the gate structure being connected via a first bottom edge of the gate structure; forming at least one source region of a first conductivity type; and forming a shielding region of a second conductivity type in contact with the first bottom edge of the gate structure across at least 20% of the gate length. Forming the shielding region includes: forming a deep shielding portion; and forming a top shielding portion between the first surface and the deep shielding portion, the top shielding portion being in contact with the first bottom edge.