Superjunction Trench Transistor Structure for Low On-State Loss
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Solution Overview
Problem
Existing semiconductor transistors with trench gate structures face challenges in optimizing channel resistance and drift region resistance while maintaining breakdown voltage.
Innovation Solution
The semiconductor device incorporates a FinFET structure with a superjunction structure, featuring gate trenches that pattern the substrate into ridges, a gate electrode insulated from the channel and current spread regions, and a superjunction structure with compensation regions of opposite conductivity types, arranged at a larger distance from the source region than the channel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a trench gate structure is used to control channel resistance, then gate control is improved, but drift region resistance increases
Solution Approach 1:
The drift region is segmented into alternating first and second doped portions with different conductivity types, creating a superjunction structure that reduces overall resistance while maintaining breakdown voltage
Solution Approach 2:
The drift region uses a composite doping structure with alternating regions of first and second conductivity types, combining the benefits of both doping types to achieve low resistance and high breakdown voltage simultaneously
2Measurement precision
If the channel region is made narrower to improve gate control, then switching precision is improved, but channel resistance increases
Solution Approach 1:
The channel region is formed with a vertical FinFET structure, adding a vertical dimension to the conduction path that increases effective channel width without compromising gate control precision
Solution Approach 2:
The gate electrode is nested within the trench, surrounding the channel region on multiple sides, which enhances gate control efficiency and allows for reduced channel dimensions without increasing resistance
3Loss of energy
If doping concentration in the channel region is increased to reduce channel resistance, then on-state losses are reduced, but breakdown voltage decreases
Solution Approach 1:
Different regions of the channel have different doping concentrations, with higher doping near the source and lower doping toward the drain, optimizing both resistance and breakdown characteristics locally
Solution Approach 2:
The doping concentration profile is optimized with a gradient from source to drain, and the superjunction structure parameters are tuned to achieve the desired balance between on-state resistance and breakdown voltage
Data Source
AI summary
A semiconductor device includes a transistor having a plurality of gate trenches formed in a semiconductor substrate, the gate trenches patterning the semiconductor substrate into ridges. The transistor further includes a gate electrode arranged in at least one of the gate trenches. A source region, a channel region and a part of a current spread region are arranged in the ridges. The semiconductor device further includes a superjunction structure arranged at a larger distance to the source region than the channel region. The superjunction structure includes a first compensation region of the first conductivity type and a second compensation region of the second conductivity type. A doping concentration of the doped portion of the second conductivity type of the channel region decreases in a second horizontal direction intersecting the first horizontal direction from a region close to the gate electrode to a central portion of the ridge.