Bidirectional Asymmetric TVS Structure for Stable Breakdown Control
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Solution Overview
Problem
Current transient voltage suppressor (TVS) devices are costly and thermally ineffective when arranged in series for high voltage applications, and low voltage TVS devices with mesa or moat termination exhibit strong deviation in breakdown voltage and high leakage current due to E-field distribution issues.
Innovation Solution
A monolithic bidirectional asymmetric TVS device is developed with a P+N−P+ structure and isolation diffusion edge termination, placing the electric field maximum in the semiconductor bulk to reduce breakdown voltage deviation and leakage current, and using mesa or moat isolation structures to further optimize E-field distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If two or more low voltage TVS diodes are arranged in series to achieve high voltage range, then the voltage range requirement is met, but the cost increases and thermal effectiveness decreases
Solution Approach 1:
The patent merges multiple TVS functions into a single monolithic device structure with P+N−P+ layers, eliminating the need for series-connected separate diodes. This integration improves thermal effectiveness by providing a common thermal path and reduces system complexity while maintaining high voltage capability through the layered semiconductor structure.
2Reliability
If low voltage TVS diodes with mesa or moat termination are used, then the device structure is simplified, but the breakdown voltage deviation increases and leakage current increases due to E-field distribution issues
Solution Approach 1:
The patent applies local quality by introducing an isolation diffusion region with specific doping characteristics at the perimeter of the N− layer. This localized modification creates an electric field maximum in the bulk semiconductor rather than at the surface, thereby stabilizing breakdown voltage and reducing leakage current in high voltage TVS applications.
3Manufacturing precision
If mesa or moat termination structures are used in high voltage TVS applications, then the manufacturing process is simplified, but the E-field distribution exhibits maximum near passivation material causing breakdown voltage deviation
Solution Approach 1:
The isolation diffusion region acts as an intermediary structure between the active TVS junction and the device perimeter. This intermediate P-type doped region modifies the electric field distribution to place the maximum in the bulk semiconductor, thereby controlling breakdown voltage with low deviation while maintaining a manufacturable structure.
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 solution provides a low deviation in breakdown voltage, low clamping voltage, and reduced power losses during surge currents, while minimizing thermal issues and leakage current, making it suitable for high voltage applications.
Implementation Method 1
the E-field distribution in such devices exhibits a maximum near a passivation material, which maximum causes a strong deviation of the breakdown voltage and a high leakage current
Implementation Method 2
a first layer, disposed on a first surface of a substrate, comprising a first P+ layer. The TVS device may also include a second layer, disposed on a second surface of the substrate, opposite the first surface, comprising a second P+ layer. As such, the TVS device may include a third layer, disposed between the first P+ layer and the second P+ layer, comprising an N− layer.
Data Source
AI summary
A transient voltage suppression (TVS) device and method of formation. A TVS device may include a first layer, disposed on a first surface of a substrate, comprising a first P+ layer; a second layer, disposed on a second surface of the substrate, opposite the first surface, comprising a second P+ layer; a third layer, disposed between the first P+ layer and the second P+ layer, comprising an N− layer; and an isolation diffusion region, comprising a P structure, connected to the second P+ layer, and extending along a perimeter of the N− layer.