Trenched Power MOSFET Breakdown Voltage via Polysilicon Trench Fill
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Solution Overview
Problem
Power semiconductor devices face a challenge in achieving a balance between reducing on-resistance for lower conduction loss and maintaining high breakdown voltage, as improvements in on-resistance often compromise structural reliability.
Innovation Solution
A trenched power semiconductor device is designed with a substrate, gate trenches, dielectric layers, polysilicon structures, and heavily doped regions, where the gate trenches are lined with a dielectric layer, and a second polysilicon structure is placed in the trench to enhance breakdown voltage, while maintaining a source metal layer connection to heavily doped regions for improved electric field distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If doping concentration and thickness of epitaxial layers are adjusted to improve on-resistance, then conduction loss is reduced, but breakdown voltage decreases and structural reliability deteriorates
Solution Approach 1:
The device is divided into multiple regions including gate trenches, body regions, source regions, and drain regions. The segmentation allows independent optimization of each region's doping concentration and thickness, enabling low on-resistance in source/drain regions while maintaining high breakdown voltage in the body region through controlled doping profiles.
Solution Approach 2:
Different regions of the semiconductor device have different doping concentrations and material compositions. The body region has optimized doping for breakdown voltage, while source and drain regions have higher doping for low on-resistance. This local quality variation allows simultaneous optimization of both conduction loss and structural reliability.
2Loss of energy
If doping concentration is increased to reduce on-resistance, then conduction loss decreases, but breakdown voltage is compromised
Solution Approach 1:
The doping concentration is varied across different regions and depths of the device. The body region maintains lower doping concentration for high breakdown voltage, while source and drain regions have higher doping concentrations for low on-resistance. This parameter change strategy enables independent control of conduction loss and breakdown voltage characteristics.
Data Source
AI summary
A trenched power semiconductor device with enhanced breakdown voltage is provided. The trenched power semiconductor device has a first trench penetrating the body region located between two neighboring gate trenches. A polysilicon structure with a conductivity type identical to that of the body region is located in a lower portion of the first trench and spaced from the body region with a predetermined distance. A dielectric structure is located on the polysilicon structure and at least extended to the body region. Source regions are located in an upper portion of the body region. A heavily doped region located in the body region is extended to the bottom of the body region. A conductive structure is electrically connected to the heavily doped region and the source region.