Lateral Super Junction JFET Layout for Higher Breakdown Voltage
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Solution Overview
Problem
Existing semiconductor devices with lateral super junction field effect transistors (JFETs) face issues with non-uniform electric field distribution, leading to lower breakdown voltage due to the field turning 90 degrees under the drain, resulting in localized electric breakdowns.
Innovation Solution
The device employs a lowermost layer of alternating conductivity type arranged as consecutive dots with varying lengths and distances, combined with deep polycrystalline trenches, to create a more uniform electric field and increase breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the bottom channel is abruptly ended at the drain with the substrate acting as a bottom gate, then the device structure is simple and easy to manufacture, but the electric field turns 90 degrees under the drain causing non-uniform field distribution and lower breakdown voltage
Solution Approach 1:
The lowermost layer is segmented into consecutive dots with different lengths and distances between them, rather than being a continuous layer. This segmentation allows the electric field to be distributed more uniformly across the drain region, preventing the 90-degree field turn that causes breakdown, while still maintaining structural simplicity and ease of manufacture.
Solution Approach 2:
The consecutive dots configuration creates local variations in the lowermost layer, where each dot region provides localized field control. The varying lengths and distances of the dots are strategically designed to address the specific field distribution needs at different locations under the drain, improving breakdown voltage without complicating the overall device structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves a higher breakdown voltage by reducing the electric field near the drain and ensuring a more uniform electric field distribution, enhancing the device's performance.
Implementation Method 1
The stack of alternating n- and p-layers will, if they are matched in charge, completely deplete each other and a uniform electric field can be formed in the material
Implementation Method 2
a lowermost layer of the first conductivity type is arranged in the form of consecutive dots with different lengths and distances between deep polycrystalline trenches of the second conductivity type in the bottom part of the JFET
Data Source
Figure 1
Figure 2
AI summary
A semiconductor device, comprising: a substrate (1) of a first conductivity type that is a base for the semiconductor device; a high voltage junction field effect transistor, JFET, over the substrate (1), wherein the JFET comprising a plurality of parallel conductive layers (p; n); a first conductive layer (n1) of the second conductivity type of the parallel conductive layers (p; n) stretching over the substrate (1, 2); wherein on top of the first conductive layer (n1) of the second conductivity type is arranged a plurality of layers forming the parallel conductive layers with channels formed by a plural- ity of doped epitaxial layers (n2-n6) of the second conductivity type with a plurality of gate layers of the first conductivity type (p1-p5) on both sides thereof; wherein a lowermost layer (p1) of the first conductivity type is arranged in the form of consecutive dots (5) with differ- ent lengths and distances (6) between them.