Lateral Transient Voltage Suppressor with Deep Isolation Trenches
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Solution Overview
Problem
Traditional transient voltage suppressors (TVS) for low-voltage applications face issues with high leakage current due to the Darlington effect when trying to reduce breakdown voltage below 2.5V, leading to potential device damage during ESD events.
Innovation Solution
A lateral transient voltage suppressor design featuring an N-type heavily doped substrate with horizontally arranged clamp diode structures and deep isolation trenches, which separates each doped well, preventing the Darlington effect and reducing leakage current, with a turned-on voltage suitable for low-voltage applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the breakdown voltage of TVS is reduced to below 2.5V for low-voltage applications, then the TVS can be triggered before device breakdown, but huge leakage current is generated due to heavy p-n junction dosage
Solution Approach 1:
The patent divides the single high-dosage p-n junction into multiple lower-dosage p-n junctions connected in series. Each junction has reduced dosage, preventing excessive leakage current while maintaining the required low breakdown voltage through cumulative effect of multiple junctions
Solution Approach 2:
The patent introduces deep isolation trenches between adjacent p-n junctions to create localized isolation regions. This allows each junction to have optimized doping characteristics without interfering with neighbors, reducing overall leakage while maintaining low breakdown voltage
2Reliability
If multiple diodes are connected in series to reduce breakdown voltage, then the turned-on voltage can be lowered, but leakage current increases due to the Darlington effect from parasitic PNP structures
Solution Approach 1:
The patent extracts and eliminates the parasitic PNP structures that cause the Darlington effect by introducing deep isolation trenches. This removes the harmful feedback path while preserving the series diode configuration for voltage reduction
Solution Approach 2:
The deep isolation trenches act as intermediary structures between adjacent p-n junctions, preventing the formation of parasitic PNP transistors by providing electrical isolation through the trench depth that exceeds the well depth
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 effectively reduces leakage current and ensures the suppressor is triggered before device breakdown, protecting electronic systems from ESD damage while maintaining low resistance for discharging ESD energy.
Implementation Method 1
deep isolation trenches arranged in the N-type heavily doped substrate and having a depth greater than depth of the clamp well. The deep isolation trenches can separate each clamp well.
Implementation Method 2
TVS devices would be triggered immediately when the ESD event is occurred. In that way, each TVS device can provide a superiorly low resistance path for discharging the transient ESD current
Implementation Method 3
The turned-on voltage of TVS in FIG. 2 is decided by the breakdown voltage of zener diode
Implementation Method 4
The turned-on voltage of TVS in FIG. 2 is decided by the breakdown voltage of zener diode 14. However, the traditional zener breakdown voltage of TVS is around 6V～10V
Data Source
AI summary
A lateral transient voltage suppressor for low-voltage applications. The suppressor includes an N-type heavily doped substrate and at least two clamp diode structures horizontally arranged in the N-type heavily doped substrate. Each clamp diode structure further includes a clamp well arranged in the N-type heavily doped substrate and having a first heavily doped area and a second heavily doped area. The first and second heavily doped areas respectively belong to opposite conductivity types. There is a plurality of deep isolation trenches arranged in the N-type heavily doped substrate and having a depth greater than depth of the clamp well. The deep isolation trenches can separate each clamp well. The present invention avoids the huge leakage current to be suitable for low-voltage application.