Semiconductor Device Column Structure Reverse Recovery
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Solution Overview
Problem
Existing semiconductor devices face challenges in managing the reverse recovery phenomenon of parasitic diodes, leading to high reverse recovery currents and capacitance, which affect switching speed and ON-resistance.
Innovation Solution
The semiconductor device incorporates a unique element structure with a first element structure having a separated first column layer and a second element structure with a second electrode, which suppresses the extension of the depletion layer during reverse recovery, reducing the rate of change in reverse recovery current and improving parasitic capacitance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional MOSFET structure is used, then the device can operate normally, but the reverse recovery current and parasitic capacitance are high, affecting switching speed
Solution Approach 1:
The semiconductor layer is divided into multiple regions with different conductivity types arranged in columns. Specifically, first conductivity type column regions and second conductivity type column regions are alternately arranged, creating a segmented structure that suppresses the extension of depletion layers during reverse recovery, thereby reducing reverse recovery current and improving switching speed
Solution Approach 2:
Different regions of the semiconductor layer are assigned different conductivity types and impurity concentrations to achieve localized optimization. The first conductivity type column regions have higher impurity concentrations than the second conductivity type column regions, creating local quality variations that control electric field distribution and reduce parasitic capacitance
2Reliability
If the depletion layer is allowed to extend freely during reverse recovery, then the parasitic diode can recover, but the rate of change in reverse recovery current increases and parasitic capacitance worsens
Solution Approach 1:
The alternating arrangement of first conductivity type and second conductivity type column regions segments the depletion layer extension path. This segmentation restricts the lateral extension of depletion layers during reverse recovery, controlling the rate of change in reverse recovery current and reducing parasitic capacitance while maintaining reliable reverse recovery characteristics
Solution Approach 2:
The second conductivity type column regions act as intermediary structures between the first conductivity type column regions. These intermediary regions with lower impurity concentrations serve as buffers that control depletion layer extension and modulate the reverse recovery process, improving overall recovery characteristics
Data Source
AI summary
A semiconductor device includes a semiconductor layer having a first surface and a second surface, an element structure formed on the first surface side of the semiconductor layer and including a first conductivity type first region and a second conductivity type second region in contact with the first region, a gate electrode opposing the second region with a gate insulating film therebetween, a first conductivity type third region formed in the semiconductor layer to be in contact with the second region, and a first electrode formed on the semiconductor layer and electrically connected to the first region and the second region, in which the element structure includes a first and a second element structure, the first element structure is separated from the second region in a direction along the first surface of the semiconductor layer, and includes a second conductivity type first column layer extending in a thickness direction.