Terminal Trench Structure for Higher Breakdown Voltage in Power Semiconductors
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Solution Overview
Problem
The edge region of power semiconductor devices with vertical structures poses a challenge in achieving high breakdown voltage due to the combined vertical and horizontal voltage stresses, which restricts the breakdown voltage of the entire device.
Innovation Solution
The semiconductor device incorporates a substrate with a main junction region, a terminal region, and a field cut-off region, featuring trenches in the terminal region near the field cut-off region. Field limiting rings are formed, with those surrounding the trenches having a greater junction depth than those not surrounding them, optimizing the electric field distribution and increasing the breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vertical structure power device is designed to achieve high withstand voltage, then the cell region can withstand high voltage, but the terminal edge region becomes a bottleneck that restricts the breakdown voltage of the whole device due to combined vertical and horizontal voltage stresses
Solution Approach 1:
The terminal region is divided into multiple segments: a first terminal region with a first doping concentration and a second terminal region with a second doping concentration. This segmentation allows different parts of the terminal region to have optimized doping profiles, enabling the device to achieve high breakdown voltage while managing the complexity of the terminal edge region through structured zonation rather than uniform design.
Solution Approach 2:
Different doping concentrations are applied to different regions: the first terminal region has a first doping concentration optimized for one direction of voltage stress, while the second terminal region has a second doping concentration optimized for another direction. This local quality approach allows each region to be tailored for its specific electrical stress conditions, resolving the contradiction between achieving high overall breakdown voltage and managing terminal edge complexity.
2Reliability
If the terminal region uses uniform doping, then the manufacturing process is simple, but the breakdown voltage is limited due to the edge effect in the terminal region
Solution Approach 1:
The doping process is optimized by applying different doping concentrations to different terminal regions. The first terminal region receives a first doping concentration and the second terminal region receives a second doping concentration. This local quality approach improves breakdown voltage by tailoring doping to specific regional needs while maintaining reasonable manufacturing complexity through a systematic two-region doping scheme rather than completely uniform or overly complex variable doping.
Solution Approach 2:
The terminal region is segmented into two distinct doped regions with different doping concentrations. This segmentation allows the manufacturing process to target specific areas with different doping parameters, achieving higher breakdown voltage through optimized local electrical properties while keeping the doping process manageable through clear regional definitions and systematic processing steps.
Data Source
AI summary
A semiconductor device includes: a substrate having a front and back surface. A main junction region, a terminal region and a field cut-off region are sequentially arranged in the substrate close to the front surface. A trench is formed in the terminal region near the field cut-off region, surrounded by field limiting rings. The junction depth of rings around the trench is greater than that of rings not surrounding it. By arranging trench structures in the terminal region, the depth of ion implantation can be increased, so that a larger junction depth can be formed subsequently. The larger junction depth can reduce a peak electric field strength on the surface; the peak electric field strength shifts from the surface to the inside of silicon; and the curvature radius of the terminal P-type implantation region is increased, thereby increasing the breakdown voltage of the terminal structure.