Diode Trench Isolation for Uniform Breakdown Voltage
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Solution Overview
Problem
The breakdown voltage performance of junction diodes is compromised by curved edges at the implant boundaries of p and n regions, and the use of floating field rings and field plates to control this performance increases device size and reduces power density.
Innovation Solution
A semiconductor device with an isolation trench that laterally surrounds the p-n junction, forming a planar junction without the need for additional area-consuming floating field rings or field plates, achieved by implanting dopants of opposite conductivity types and forming an isolation trench through the semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If floating field rings and field plates are provided above the curved edges of the implanted regions to control diode breakdown voltage performance, then the breakdown voltage performance is improved, but the device area increases significantly
Solution Approach 1:
The patent extracts and removes the floating field rings and field plates from the device structure, replacing them with an isolation trench that extends through the semiconductor layer. This eliminates the area-consuming components while maintaining breakdown voltage control through the trench structure that laterally surrounds the p-n junction and creates a planar junction interface.
Solution Approach 2:
The patent transitions from a two-dimensional surface-based solution (floating field rings and field plates on the surface) to a three-dimensional vertical structure (isolation trench extending through the semiconductor layer). This dimensional change allows the trench to laterally surround and control the junction edges without requiring additional surface area, thus improving breakdown voltage performance while maintaining compact device footprint.
2Reliability
If floating field rings and field plates are used to control diode breakdown voltage, then the breakdown voltage uniformity is improved, but the power density decreases due to increased device size
Solution Approach 1:
The patent removes the floating field rings and field plates that were consuming device area without contributing to active device operation. The isolation trench replaces these extracted components, providing breakdown voltage uniformity control while preserving the active device area for power-generating functions, thus maintaining high power density.
Solution Approach 2:
The isolation trench serves multiple functions: it provides mechanical support, electrical isolation, and breakdown voltage uniformity control through the planar junction it creates. This multi-functionality eliminates the need for separate floating field rings and field plates, allowing the same structure to both control breakdown voltage and maximize power density by not consuming additional device area.
3Device complexity
If curved edges at the implant boundaries are present, then the device structure is simpler, but the breakdown voltage performance deteriorates
Solution Approach 1:
The patent segments the semiconductor layer by introducing an isolation trench that divides and laterally surrounds the p-n junction. This segmentation creates a planar junction interface within the trench, eliminating the curved edge effects at implant boundaries while maintaining overall structural simplicity. The trench acts as a boundary that straightens the junction interface without requiring complex additional structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The planar junction provides enhanced breakdown voltage performance and allows for compact device designs with increased power density without the size increases associated with floating field rings.
Implementation Method 1
The isolation trench extends through the first and second portions of the semiconductor layer and laterally surrounds the first and second nodes, forming a planar junction that enhances breakdown voltage performance
Data Source
AI summary
A semiconductor device includes a semiconductor layer over a semiconductor substrate with adjacent first and second portions, the first portion having a first conductivity type, and the second portion having a second, opposite, conductivity type, and an isolation trench extending through first and second portions and laterally surrounding the first and second portions of the semiconductor layer. A method includes implanting dopants of a first conductivity type in a first portion of a semiconductor layer, implanting dopants of a second, opposite, conductivity type in a second portion of the semiconductor layer that is adjacent to the first portion, and forming an isolation trench that extends through and laterally surrounds the first and second portions to form a junction between the interior portions of the first and second portions within the isolation trench that is approximately planar.