Anchored Air-Gap Field Plate Trenches for Trench MOSFET Breakdown
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Solution Overview
Problem
Current power MOSFET designs face limitations in achieving high breakdown voltage with low drift layer resistance, necessitating an improved field plate structure for enhanced performance.
Innovation Solution
The semiconductor device incorporates field plate trenches with air gaps separating the field plates from the substrate, anchored by an electrically insulative material that spans the air gap to the substrate bottom, optimizing breakdown voltage and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If field plate is directly contacted with trench walls and bottom, then manufacturing is simpler, but electric field distribution is degraded and breakdown voltage is reduced
Solution Approach 1:
The field plate structure is segmented from the trench walls and bottom by introducing air gaps through selective etching. This segmentation creates isolated regions that improve electric field distribution while maintaining manufacturing feasibility through a systematic multi-step process
Solution Approach 2:
Material is extracted from the trench structure to create air gaps between the field plate and trench walls/bottom. This removal of material (silicon or silicon oxide) establishes the necessary separation to enhance breakdown voltage without complicating the overall fabrication process
2Stability of the object's composition
If field plate is anchored with conductive material, then mechanical stability is improved, but electrical insulation is compromised
Solution Approach 1:
An intermediary material (silicon oxide or silicon nitride) is introduced between the field plate and trench bottom to provide both mechanical anchoring and electrical insulation. This mediator resolves the contradiction by simultaneously fulfilling both mechanical and electrical requirements
Solution Approach 2:
The anchoring structure uses composite material composition combining insulating materials (silicon oxide, silicon nitride) with the field plate. This composite approach achieves both mechanical stability through adhesion and electrical insulation through the inherent properties of the insulating material
3Reliability
If field plate is fully surrounded by dielectric material, then electrical insulation is maximized, but electric field stabilization is reduced
Solution Approach 1:
The dielectric material is segmented to create discrete air gap regions rather than continuous surrounding. This segmentation allows the field plate to maintain electrical insulation where needed while creating controlled electric field distribution in the air gap regions
Data Source
AI summary
A semiconductor device includes: a semiconductor substrate; a first gate trench and a second gate trench both extending from a first main surface of the semiconductor substrate into the semiconductor substrate; a semiconductor mesa delimited by the first and second gate trenches; and a field plate trench extending from the first main surface through the semiconductor mesa. The field plate trench includes a field plate separated from each sidewall and a bottom of the field plate trench by an air gap. The field plate is anchored to the semiconductor substrate at the bottom of the field plate trench by an electrically insulative material that occupies a space in a central part of the field plate, the electrically insulative material spanning the air gap to contact the semiconductor substrate at the bottom of the field plate trench. Methods of producing the semiconductor device are also described.