SiC Trench Gate Structure With Field Plate for Breakdown Stability
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Solution Overview
Problem
Silicon carbide (SiC) power devices face challenges in maintaining breakdown voltage and reliability due to electric field concentration and dielectric breakdown risks in the gate insulating film, as well as issues with moisture penetration and mechanical strength.
Innovation Solution
A semiconductor device design featuring a silicon carbide layer with a trench gate structure, a field plate with lower resistivity than the inter-layer insulating film, and p-type layers to relax electric field concentration and enhance moisture resistance, including a thick inter-layer insulating film to improve mechanical strength and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gate insulating film is used in SiC power devices, then the device can operate, but breakdown voltage fluctuates and reliability decreases due to electric field concentration
Solution Approach 1:
A field plate structure is introduced as an intermediary element between the gate electrode and the drain region. This field plate, positioned on the drain side, acts as a mediator to distribute and relax the concentrated electric field in the gate insulating film, thereby preventing dielectric breakdown and stabilizing breakdown voltage.
Solution Approach 2:
The patent modifies the electrical parameters of the device by introducing a field plate with specific resistivity characteristics. The field plate changes the electric field distribution parameters, reducing peak field concentration and altering the potential gradient in the gate insulating film to prevent breakdown.
2Strength
If conventional structures are used, then manufacturing is simple, but moisture penetration occurs and mechanical strength decreases
Solution Approach 1:
The patent employs a composite structure combining the field plate, inter-layer insulating film, and gate insulating film. This multi-layer composite design provides both mechanical reinforcement to improve strength and moisture barrier properties to prevent penetration, addressing both requirements simultaneously.
3Strength
If the inter-layer insulating film is made thicker to improve mechanical strength, then strength increases, but device complexity increases
Solution Approach 1:
The field plate structure serves multiple functions simultaneously: it relaxes electric field concentration to prevent dielectric breakdown, provides mechanical reinforcement to improve strength, and acts as a moisture barrier. This multi-functionality allows thickness optimization without proportionally increasing complexity.
Data Source
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AI summary
A silicon carbide layer includes a first surface, a second surface, a third surface positioned at a side opposite to the first and second surfaces in a first direction, and a side surface. The second surface is at a position recessed further toward the third surface side than the first surface. An inter-layer insulating film is located on the second surface. A thickness of the inter-layer insulating film is greater than a difference in heights in the first direction between the first surface and the second surface. A field plate is located in the inter-layer insulating film. The field plate has a lower resistivity than the inter-layer insulating film.