Vertical JFET Trench Layout for Breakdown-Stable Edge Termination
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Solution Overview
Problem
Current semiconductor devices, such as junction field effect transistors (JFETs), face challenges in optimizing area-specific on-state resistance and reliability, particularly in balancing electric breakdown capability and device functionality as device geometries shrink.
Innovation Solution
A vertical junction field effect transistor (VJFET) design featuring alternating mesa regions and trench structures with varying widths and depths, where the width of trench structures decreases towards the edge termination area, and the trench depth also decreases, to reduce electric field curvature and enhance voltage stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If device geometries are shrunk to reduce costs and increase device functionalities per unit area, then area-specific on-state resistance improves, but reliability and electric breakdown capability deteriorate
Solution Approach 1:
The patent applies local quality by creating a non-uniform trench structure where the trench width varies along its length. The trench is narrower at the edge termination area and wider in the central region, allowing different sections to serve different functions: the narrower edge section improves voltage stabilization and breakdown capability, while the wider central section maintains low on-state resistance. This spatial variation in geometry resolves the contradiction between reliability and area-specific resistance.
Solution Approach 2:
The patent changes the geometric parameters of the trench structure, specifically varying the trench width as a function of position along the trench length. By continuously or stepwise adjusting the trench width parameter, the design optimizes both the electric field distribution (improving breakdown capability) and the conductive path (maintaining low on-state resistance), thus resolving the technical contradiction.
2Ease of manufacture
If trench structures with uniform width are used, then manufacturing is simplified, but voltage stabilization and electric breakdown capability are reduced
Solution Approach 1:
The trench structure implements local quality by having different widths in different regions. The edge termination area features a narrower trench width to enhance voltage stabilization and breakdown capability, while the central area has a wider trench width. This localized geometric variation improves reliability without requiring complete redesign of the entire trench structure.
Solution Approach 2:
The trench structure is segmented into multiple sections with different width characteristics. The trench can be divided into an edge section with narrower width and a central section with wider width, allowing each segment to be optimized for its specific function while maintaining overall structural integrity and manufacturability.
Data Source
AI summary
A vertical junction field effect transistor includes mesa regions and trench structures extending along a first lateral direction in a semiconductor body and arranged alternately along a second lateral direction. The trench structures include a gate contact material electrically connected to a gate region of a first conductivity type in the semiconductor body. A width of the trench structures satisfies one or more of the following conditions: i) the width of at least one trench structure arranged outermost along the second lateral direction is smaller than in a more central part of the trench structures; or ii) the width of at least some trench structures is smaller along an end part in the first lateral direction than in the more central part, an extent of the end part along the first lateral direction being larger than a pitch between neighboring trench structures along the second lateral direction.