Trench Termination Structure for MOSFET Breakdown Voltage Stability
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving desired breakdown voltage (BVdss) in metal oxide semiconductor (MOS) field effect transistors (FETs) due to issues with trench termination structures and shield plate designs, leading to unstable breakdown voltages and reduced robustness against surge currents.
Innovation Solution
The implementation of a semiconductor device structure with alternately connected and disconnected active trenches to a termination trench, along with specific trench end and corner designs that form a substantially uniform electric field, enhances charge balance and depletion spread, thereby improving breakdown voltage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional trench termination structures are used, then device complexity is reduced, but breakdown voltage stability deteriorates
Solution Approach 1:
The invention segments the trench termination structure into multiple discrete trenches rather than using a continuous termination region. This segmentation allows for better control of electric field distribution and charge balance, improving breakdown voltage stability while maintaining manageable device complexity through systematic arrangement of individual trenches
Solution Approach 2:
The invention applies different trench configurations to different regions of the device. Specifically, trenches are positioned with specific spacing relationships to active areas versus other regions, creating local variations in termination structure that optimize breakdown voltage stability in critical areas without unnecessarily complicating the entire device structure
2Reliability
If shield plate structure is added to improve breakdown voltage, then breakdown voltage increases, but device complexity increases
Solution Approach 1:
The invention extracts or removes the shield plate structure from the device design, relying instead on optimized trench termination configurations to achieve the desired breakdown voltage. This eliminates the additional complexity introduced by shield plates while maintaining or improving breakdown voltage performance through careful trench spacing and positioning
Solution Approach 2:
The trench structures serve multiple functions: they provide termination for the electric field, establish charge balance in the drift region, and define device geometry. By making the trenches multi-functional, the invention eliminates the need for separate shield plate structures, thereby reducing device complexity while maintaining breakdown voltage performance
3Reliability
If uniform trench spacing is used, then manufacturing precision is simplified, but breakdown voltage performance deteriorates due to under-depletion or over-depletion
Solution Approach 1:
The invention implements non-uniform trench spacing where trenches are positioned at specific distances from active areas versus other regions. This local differentiation ensures proper charge balance and depletion characteristics in critical regions without requiring precision control throughout the entire device, thereby improving breakdown voltage performance while relaxing manufacturing precision requirements
Solution Approach 2:
The invention changes the spacing parameter from uniform to non-uniform distribution. By varying trench spacing based on location relative to active areas, the invention optimizes depletion characteristics and breakdown voltage performance while creating a design that is more tolerant of manufacturing variations in less critical regions
4Reliability
If termination space is adjusted for different epi doping levels, then breakdown voltage performance improves, but ease of manufacture deteriorates
Solution Approach 1:
The invention establishes fixed trench spacing parameters that are optimized to work across a range of epi doping levels. By designing the trench configuration with inherent robustness to doping variations, the invention maintains breakdown voltage performance without requiring manufacturer adjustments to termination space for different doping specifications, thereby improving ease of manufacture
Data Source
AI summary
In an embodiment, a method of forming a semiconductor may include forming a plurality of active trenches and forming a termination trench substantially surrounding an outer periphery of the plurality of active trenches. The method may also include forming at least one active trench of the plurality of active trenches having corners linking trench ends to sides of active trenches wherein each active trench of the plurality of active trenches has a first profile along the first length and a second profile at or near the trench ends; and forming a termination trench substantially surrounding an outer periphery of the plurality of active trenches and having a second profile wherein one of the first profile or the second profile includes a non-linear shape.