Fin-FET Power Transistor with Segmented Doping for Bidirectional Blocking
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Solution Overview
Problem
Conventional power switch transistors have high on-resistance and limited bidirectional breakdown voltage due to unidirectional conductivity, requiring complex structures like paired transistors to achieve bidirectional turn-off, which complicates control and increases on-resistance.
Innovation Solution
A power transistor device with a substrate structure featuring fin portions and multiple conductive layers, including shielding gates, that expand the current channel width and reduce on-resistance by enhancing carrier concentration control, while maintaining high bidirectional voltage capability through strategically placed dielectric and spacer layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional transistor structure with body diode is used, then unidirectional conductivity is achieved, but bidirectional voltage withstanding capability is limited and control complexity increases
Solution Approach 1:
The transistor channel is segmented into multiple regions with different doping concentrations (first doped region, second doped region, third doped region) along the current flow direction. This segmentation enables different functional zones: the first doped region provides low resistance for forward conduction, while the second and third doped regions with higher doping concentrations form depletion regions that block reverse voltage, achieving bidirectional voltage withstanding without requiring paired transistors
Solution Approach 2:
Different regions of the transistor are assigned different doping concentrations to perform different functions. The first doped region has lower doping concentration to reduce on-resistance during conduction, while the second and third doped regions have higher doping concentrations to form effective depletion barriers for reverse voltage blocking. This local quality differentiation enables the single transistor to achieve both low on-resistance and bidirectional voltage withstanding capability
2Reliability
If paired transistors connected in series are used to achieve bidirectional turn-off, then bidirectional voltage withstanding is improved, but on-resistance increases and control is complicated
Solution Approach 1:
The patent merges the functions of multiple transistors into a single transistor device. By integrating multiple doped regions within one transistor structure, the device achieves bidirectional voltage withstanding capability that previously required paired transistors, while reducing the total on-resistance since current flows through a single continuous channel rather than through series-connected multiple transistors
3Device complexity
If conventional transistor structure is used, then simple structure is maintained, but on-resistance is high and bidirectional voltage capability is limited
Solution Approach 1:
The channel is divided into segmented doped regions with varying concentrations. The first doped region with lower concentration reduces on-resistance for low loss during conduction, while maintaining an overall simple single-transistor structure that is easier to control than paired transistor configurations
Solution Approach 2:
The doping concentration parameter is varied across different regions of the transistor. By changing the doping concentration from low in the first doped region to high in the second and third doped regions, the patent optimizes both on-resistance and voltage blocking capability within a simple single-transistor structure
Data Source
AI summary
Provided is a power transistor device including a substrate structure, a first conductive layer, a second conductive layer and a third conductive layer. The substrate structure has a base portion and fin portions. The fin portions protrude from a surface of the base portion and extend along a first direction. The first conductive layer is disposed across the fin portions and extends along a second direction different from the first direction. The second conductive layer is disposed across the fin portions, is located at one side of the first conductive layer and extends along the second direction. The first spacer is disposed between and in physical contact with the first conductive layer and the second conductive layer.