TVS Diode Epitaxial Segmentation for Low Capacitance
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Solution Overview
Problem
Current transient-voltage-suppression (TVS) diode devices face challenges in reducing capacitance while maintaining a simplified and low-cost manufacturing process, and shrinking the area occupied by the TVS chips.
Innovation Solution
The TVS diode device is constructed using two thin epitaxial layers formed by epitaxial growth processes, with trench isolation features and specific doping processes to create a Zener diode with stable reverse breakdown voltage, low leakage current, and low capacitance, allowing for efficient transient voltage suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional TVS diode device configurations are used, then the manufacturing process is simplified and cost is reduced, but capacitance cannot be sufficiently reduced
Solution Approach 1:
The device divides the active region into multiple discrete doped well regions (first conductivity type and second conductivity type) separated by trench isolation features. This segmentation allows each region to contribute differently to the overall capacitance while maintaining the voltage suppression function, thereby reducing total capacitance without overly complicating the manufacturing process.
Solution Approach 2:
Different regions of the device are doped with different conductivity types and concentrations to create localized electrical properties. The first conductivity type doped well regions and second conductivity type doped well regions have distinct doping characteristics that optimize the breakdown voltage and capacitance distribution across the device structure.
2Area of moving object
If the TVS chip area is reduced, then integration density improves, but manufacturing precision and control become more difficult
Solution Approach 1:
The device utilizes vertical layering with multiple epitaxial layers grown at different depths, rather than expanding horizontally. The trench isolation features extend vertically into the substrate, and doped well regions are positioned at different vertical levels, allowing compact horizontal footprint while maintaining sufficient manufacturing control through precise vertical epitaxial growth and doping processes.
Solution Approach 2:
Multiple functional regions are nested within the compact chip structure, with doped well regions positioned within epitaxial layers that are themselves contained within the substrate. The trench isolation features nest between active regions, allowing maximum utilization of the chip area while maintaining manufacturability through systematic layering.
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 achieves a stable reverse breakdown voltage, low leakage current, and low capacitance, effectively protecting high-frequency circuits from electrostatic discharge and transient voltage overstress, while simplifying the fabrication process and reducing costs.
Implementation Method 1
A second conductivity type first epitaxial layer is disposed over the substrate... A second conductivity type second epitaxial layer is disposed between the second conductivity type first epitaxial layer and the substrate
Implementation Method 2
A first conductivity type doped well region is disposed in the second conductivity type second epitaxial layer... A first conductivity type buried layer is disposed in the second conductivity type second epitaxial layer
Implementation Method 3
The second conductivity type doped well region and the first conductivity type buried layer collectively form a Zener diode... the operating circuit's voltage is clamped to a predetermined maximum clamping voltage
Data Source
AI summary
A transient-voltage-suppression (TVS) diode device and a method of fabricating the same are disclosed. The TVS diode device includes a substrate. A second conductivity type first epitaxial layer is disposed over the substrate. A second conductivity type second epitaxial layer is disposed between the second conductivity type first epitaxial layer and the substrate. A plurality of trench isolation features divides the substrate into a first active region including a second conductivity type doped well region disposed in the second conductivity type first epitaxial layer. A first conductivity type doped well region and a first conductivity type buried layer are disposed in the second conductivity type second epitaxial layer. The second conductivity type doped well region and the first conductivity type buried layer collectively form a Zener diode.