Shielded Gate MOSFET Termination Trenches for Breakdown Voltage
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Solution Overview
Problem
High power semiconductor devices, such as shielded gate MOSFETs, face challenges in maintaining high breakdown voltage due to charge imbalance and electric field concentration at the ends of shielded gate electrodes, leading to rapid depletion and voltage breakdown in the termination region.
Innovation Solution
The implementation of tapered trench structures with conductive electrodes and dielectric linings, including features like tabs and reverse tapers, helps distribute charge and reduce electric field strength, thereby increasing the breakdown voltage by modifying the trench pattern and shape in the termination region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If shielded gate electrodes are used in high power semiconductor devices, then device power handling capability is improved, but charge imbalance and electric field concentration occur at the ends of shielded gate electrodes leading to reduced breakdown voltage
Solution Approach 1:
The patent applies local quality by modifying only the termination region of the shielded gate electrode while maintaining the standard structure in the active region. The trench is tapered specifically in the termination region to distribute charge and reduce electric field concentration, without altering the electrode structure in the power-handling active region.
Solution Approach 2:
The patent introduces a dimensional change by transitioning from a vertical trench structure to a tapered trench structure in the termination region. This geometric modification in the longitudinal dimension allows for gradual charge distribution and reduces the electric field concentration at the electrode ends.
2Ease of manufacture
If uniform trench structures are used throughout the device, then manufacturing simplicity is maintained, but electric field concentration occurs at termination regions reducing device reliability
Solution Approach 1:
The patent implements local quality by applying the tapered trench structure only in the termination region where electric field concentration occurs, while maintaining uniform vertical trenches in the active region. This localized modification addresses the reliability issue without complicating the overall manufacturing process.
Solution Approach 2:
The patent segments the trench structure into two distinct regions: a vertical trench portion in the active region and a tapered trench portion in the termination region. This segmentation allows each region to be optimized for its specific function while using standard manufacturing techniques for each segment.
3Area of stationary object
If shielded gate electrodes extend fully into termination regions, then device area utilization is improved, but charge imbalance causes rapid depletion and voltage breakdown
Solution Approach 1:
The patent uses dimensional change by tapering the trench in the longitudinal dimension as it extends into the termination region. This gradual narrowing allows the electrode to occupy termination region area while simultaneously distributing charge to prevent breakdown, resolving the conflict between area utilization and reliability.
Solution Approach 2:
The patent changes the geometric parameter of the trench from a constant cross-section to a varying cross-section in the termination region. This parameter change in trench width along the longitudinal axis enables area utilization while preventing charge imbalance through gradual field distribution.
Data Source
AI summary
Shielded gate semiconductor devices are disclosed for use in high power applications such as electric vehicles and industrial applications. The devices are formed as mesa (106)/trench (400) structures in which shielded gate electrodes are formed in the trenches. Various trench structures (400, 500, 600, 700) are presented that include tapered portions (401) and end tabs (502, 602, 702, 802) that can be beneficial in managing the distribution of electric charge and associated electric fields. The tapered trenches (400) can be used to increase and stabilize breakdown voltages in a termination region (104) of a semiconductor die (100).