Trench IGBT Gate Capacitance Reduction via Segmented Electrodes
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Solution Overview
Problem
Trench IGBT structures have a large unwanted gate capacitance, which hinders high-speed switching in power semiconductor devices, despite efforts to minimize it through various split-poly gate structures.
Innovation Solution
A power semiconductor device design featuring symmetric trench structures with insulated top and bottom electrodes, a shallower second conductivity type body region, and a higher impurity concentration in the first conductivity type well region, which reduces gate capacitance and enhances switching speed by eliminating the channel region adjacent to certain trench structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a trench IGBT structure is used, then the device can withstand high voltage and high current operation, but the gate capacitance becomes large which reduces switching speed
Solution Approach 1:
The gate electrode is divided into multiple segments (first gate electrode and second gate electrode) separated by a first conductivity type source region. This segmentation reduces the total gate capacitance by dividing the capacitive load into smaller portions, thereby improving switching speed while maintaining the trench structure's voltage and current withstanding capability
Solution Approach 2:
Different regions of the gate structure are assigned different conductivity types and functions. The first gate electrode has second conductivity type and is separated from the second gate electrode (first conductivity type) by a source region. This local differentiation optimizes the electrical characteristics in different areas, reducing overall gate capacitance while preserving the high-voltage blocking capability of the trench structure
2Quantity of substance
If various split-poly gate structures are proposed to reduce gate capacitance, then gate capacitance is reduced, but the switching speed becomes lower
Solution Approach 1:
The gate structure employs dynamic control through separate gate electrodes that can be independently biased. The first and second gate electrodes can be applied with different potentials, allowing dynamic optimization of the electric field distribution during switching transitions. This dynamic control enables faster switching speeds compared to static split-poly structures while maintaining reduced gate capacitance
Solution Approach 2:
The gate structure is designed with preliminary field distribution through the segmented electrodes and source regions. Before the main switching action occurs, the electric field is pre-configured through the separate gate electrodes, reducing the time required for charge redistribution during switching. This preliminary field arrangement enables faster switching speeds compared to conventional structures
Data Source
AI summary
A power semiconductor device includes a semiconductor substrate, trench structures comprising a first, a second, a third and a fourth trench structure formed in the substrate, a second conductivity type body region formed between the trench structures, a first conductivity type source region formed in the second conductivity type body region, and an emitter electrode and a gate pad formed over the substrate, wherein each trench structure includes a top electrode and a bottom electrode, and each top electrode is insulated from the corresponding bottom electrode, and wherein the first trench structure is symmetric to the fourth trench structure, and the second trench structure is symmetric to the third trench structure, and wherein the first trench structure is not identical to the second trench structure, and wherein no first conductivity type source region is formed to be adjacent to the second trench structure and the third trench structure.