Trench-Gate Transistor Doping Profile for Wider SiC Ridges
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Solution Overview
Problem
Current semiconductor transistors with gate electrodes in trenches adjacent to channel regions face challenges in optimizing characteristics, particularly in silicon carbide substrates, where improving conductivity and mobility while maintaining normal off-state performance is difficult.
Innovation Solution
The semiconductor device features gate trenches that pattern the substrate into ridges, with a gate electrode insulated from the channel and drift regions, and a doping profile that decreases in concentration from the edge to the center of the ridge, enhancing conductivity and mobility by increasing electron density and mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate trenches are formed in the semiconductor substrate, then the transistor can be structured with gate electrode insulated from channel region, but the manufacturing complexity increases
Solution Approach 1:
The gate structure is segmented into multiple gate trenches formed in the semiconductor substrate, with each trench containing a gate electrode. This segmentation allows the gate to be insulated from the channel region while maintaining effective control, resolving the contradiction between improved transistor characteristics and manufacturing complexity by creating discrete, manageable structural units.
Solution Approach 2:
An insulating layer is introduced as an intermediary between the gate electrode and the channel region within the gate trenches. This intermediary structure provides the necessary electrical insulation while allowing the gate to maintain its control function, thus improving reliability without making the device unusable despite the increased structural complexity.
2Ease of manufacture
If doping concentration is uniform across the ridge, then manufacturing is simpler, but conductivity and mobility are reduced for larger ridge widths
Solution Approach 1:
The doping concentration is varied locally across the ridge width, with higher concentrations near the gate electrode and lower concentrations toward the central portion. This local quality variation optimizes conductivity and mobility in different regions of the ridge, allowing larger ridge widths to maintain high performance while keeping the manufacturing process relatively simple through controlled doping gradients.
Solution Approach 2:
The doping concentration parameter is changed across the ridge width rather than remaining uniform. By implementing a doping gradient that decreases from the edge near the gate electrode to the central portion, the transistor achieves enhanced conductivity and mobility for larger ridge widths while maintaining manufacturing feasibility through standard doping techniques.
3Quantity of substance
If ridge width is increased, then more current can be handled, but electron mobility decreases with uniform doping
Solution Approach 1:
Different regions of the ridge are assigned different doping qualities: regions near the gate electrode have higher doping concentrations to support higher current densities, while central regions have lower concentrations to maintain electron mobility. This local differentiation allows the ridge to handle increased current while preserving high electron mobility throughout the structure.
Solution Approach 2:
The doping concentration parameter is varied across the ridge width to simultaneously achieve high current capacity and maintained electron mobility. The gradient doping profile allows larger ridge widths to carry more current while the reduced central doping preserves electron mobility, resolving the contradiction between quantity of charge carriers and their mobility speed.
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 design improves transistor characteristics by maintaining normal off-state performance while providing high conductivity and enhanced mobility, even for larger ridge widths, and increases short-circuit robustness.
Implementation Method 1
doping a portion of the ridges with dopants of a second conductivity type so that a doping concentration of the doped portion 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
Data Source
AI summary
A semiconductor device includes a transistor. The transistor includes gate trenches formed in a semiconductor substrate, extending in a first horizontal direction and patterning the semiconductor substrate into ridges. The ridges are arranged between two adjacent gate trenches, respectively. The transistor further includes a gate electrode arranged in at least one of the gate trenches, a source region of a first conductivity type, a channel region, and a drift region of the first conductivity type. The source region, channel region and a part of the drift region are arranged in the ridges. The gate electrode is insulated from the channel region and the drift region. The channel region includes a doped portion of a second conductivity type. A doping concentration of the doped portion 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.