Asymmetric TVS Structure for Stable High-Voltage Breakdown
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Solution Overview
Problem
Current transient voltage suppressor (TVS) devices are not suitable for high voltage applications due to E-field distribution issues causing breakdown voltage deviation and high leakage current, and existing solutions like series connections are costly and thermally ineffective.
Innovation Solution
A monolithic bidirectional asymmetric TVS device with a P+N+ structure and back-sided isolation diffusion edge termination, which places the electric field maximum in the semiconductor bulk, reducing breakdown voltage deviation and leakage current, and using mesa or moat isolation structures to further optimize the device's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mesa or moat termination structures are used in low voltage TVS diodes, then the device structure is simple and manufacturing is easy, but the E-field distribution exhibits maximum near passivation material causing strong deviation of breakdown voltage and high leakage current
Solution Approach 1:
The patent applies asymmetry by implementing different termination structures on opposite sides of the semiconductor substrate. The first surface has a mesa or moat termination with passivation, while the second surface has a diffused termination without passivation. This asymmetric design shifts the E-field maximum into the bulk semiconductor material rather than concentrating it near passivation edges, thereby reducing breakdown voltage deviation while maintaining manufacturing simplicity.
Solution Approach 2:
The patent applies local quality by creating different termination characteristics at different locations on the substrate. The first surface termination (with passivation) differs from the second surface termination (diffused, without passivation). This localized differentiation allows the E-field distribution to be optimized in the bulk region while maintaining simple manufacturing processes at each location.
2Reliability
If two or more low voltage TVS diodes are arranged in series to achieve high voltage range, then the breakdown voltage range is extended, but the device complexity increases and thermal effectiveness decreases
Solution Approach 1:
The patent merges multiple functions into a single monolithic device structure. Instead of using separate low voltage TVS diodes connected in series, the invention integrates a high voltage TVS function directly into one semiconductor substrate with asymmetric terminations. This combination achieves the desired high voltage range (500V-1000V) while reducing device complexity and improving thermal effectiveness through a unified structure.
Solution Approach 2:
The patent transitions from a planar arrangement of multiple discrete devices to a three-dimensional monolithic structure with asymmetric terminations on opposite surfaces. This dimensional change allows the E-field to be distributed through the bulk of the substrate, achieving high voltage capability without requiring series connections of multiple low voltage devices.
3Device complexity
If mesa or moat termination structures are used, then the device structure is simple, but the leakage current is high due to E-field concentration near passivation material
Solution Approach 1:
The patent uses asymmetry to eliminate the harmful effect of E-field concentration. By implementing a diffused termination on the second surface without passivation, the E-field maximum is shifted into the bulk semiconductor material. This asymmetric configuration maintains structural simplicity while dramatically reducing leakage current compared to symmetric mesa or moat terminations on both surfaces.
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 TVS device with low clamping voltage, low power losses during surge currents, and a low thermal coefficient, effectively addressing the limitations of existing TVS devices by maintaining a stable breakdown voltage and reducing leakage current.
Implementation Method 1
forming an isolation diffusion region along a perimeter of the N- substrate, comprising a P- material, by diffusing a P-type dopant from a second main surface of the N- substrate
Implementation Method 2
Bidirectional asymmetric transient voltage suppressor device
Data Source
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Figure 2A
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.