High-Voltage Transistor Fabrication With Trench Etching
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Solution Overview
Problem
Lateral power devices, such as MOSFETs and JFETs, have limited current-carrying capability due to the restricted active channel area at the surface, which hinders their ability to switch high voltages effectively while maintaining compatibility with integrated circuit fabrication techniques.
Innovation Solution
The use of trench etching technology to form sidewall-gated JFETs and depletion mode MOSFETs, where trenches extend deep into the semiconductor material, increasing the active channel area and enhancing current-switching capability without compromising process compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lateral power devices are used to maintain process compatibility with integrated circuit fabrication techniques, then ease of manufacture is improved, but current-carrying capability deteriorates due to limited active channel area
Solution Approach 1:
The patent transitions from a two-dimensional surface channel to a three-dimensional vertical channel by etching trenches into the semiconductor substrate. The gate electrode is positioned on the sidewalls of the trench, creating a vertical field-effect transistor where the channel extends deep into the substrate rather than remaining confined to the surface. This dimensional change dramatically increases the active channel area while preserving lateral device fabrication compatibility.
2Quantity of substance
If the active channel area is increased to improve current-switching capability, then current-switching capability is improved, but device complexity increases due to additional trench etching steps
Solution Approach 1:
The trench structure serves multiple functions simultaneously: it defines the channel region, provides sidewall surfaces for gate electrode formation, enables vertical channel extension, and creates natural isolation between adjacent devices. The gate electrode on the trench sidewalls performs both the gating function and defines the channel boundaries. This multi-functionality reduces the need for separate structural elements and simplifies the overall device architecture despite the added etching step.
Data Source
AI summary
A lateral high-voltage depletion-mode device structure in which fingers of semiconductor material are interdigitated with trench gates. Since the effective channel area is proportional to the depth of the trenches, a large amount of active channel area can be achieved for a given surface area.