Bidirectional Zener Diode Base Region Dimension Optimization
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Solution Overview
Problem
The existing TVS devices with an nppn layered structure require multiple pn junctions, leading to a complex manufacturing process and increased costs, while simplifying the structure to form only a pair of pn junctions in the surficial portion of the substrate results in higher leakage current when aiming for low reverse breakdown voltage and stand-off voltage.
Innovation Solution
A bidirectional Zener diode is designed with a substrate having a first and second conductivity type impurity region formed in a surficial portion to create pn junctions, with a base region dimension between them set to 4.0 μm to 12.5 μm, allowing for a simple structure and effective electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple pn junctions are formed in an nppn layered structure, then the reverse breakdown voltage and stand-off voltage can be reduced, but the manufacturing process becomes complex and costs increase
Solution Approach 1:
The patent merges multiple pn junctions into a single substrate surface structure. Instead of forming separate nppn layers with multiple junctions, the invention creates a single p-type substrate with multiple n-type impurity regions formed on its surface, achieving the same electrical function with simplified structure and manufacturing.
Solution Approach 2:
The patent transitions from a vertical layered structure (nppn with multiple junctions in the depth direction) to a horizontal surface structure (multiple impurity regions on the substrate surface). This dimensional change simplifies the manufacturing process while maintaining the required electrical characteristics.
2Ease of manufacture
If the structure is simplified to form only a pair of pn junctions in the surficial portion, then the manufacturing process is simplified, but the leakage current increases
Solution Approach 1:
The patent applies local quality by creating n-type impurity regions with specific characteristics at particular locations on the p-type substrate surface. Each impurity region has controlled doping concentration and geometry, allowing localized optimization of electrical properties to reduce leakage current while maintaining manufacturing simplicity.
Solution Approach 2:
The patent controls leakage current by adjusting parameters such as the dimension of the base region (4.0 μm to 12.5 μm), doping concentrations, and impurity region geometries. These parameter changes optimize the electrical characteristics without complicating the manufacturing process.
3Volume of moving object
If the base region dimension is reduced, then the device size is minimized, but the leakage current increases and electrical performance deteriorates
Solution Approach 1:
The patent optimizes the base region dimension to a specific range (4.0 μm to 12.5 μm) to achieve the best balance between device miniaturization and electrical performance. This parameter optimization ensures low leakage current while maintaining compact device size.
Solution Approach 2:
The patent compensates for the small base region size by creating optimally designed n-type impurity regions with specific doping concentrations and geometries. These localized quality enhancements ensure proper electrical performance despite the reduced overall device size.
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 bidirectional Zener diode achieves a reverse breakdown current of 100 μA to 10 mA, reverse breakdown voltage of 6 V to 7 V, and reverse stand-off voltage of 3 V to 5 V, with a leakage current of less than 10 nA, while maintaining a cost-effective manufacturing process.
Implementation Method 1
A second conductivity type first impurity region is formed in a surficial portion of the base region so as to form a pn junction between the first impurity region and the base region
Implementation Method 2
A second conductivity type second impurity region is formed in a surficial portion of the base region in a manner spaced apart from the first impurity region so as to form a pn junction between the second impurity region and the base region
Data Source
AI summary
A bidirectional Zener diode includes a substrate. A first conductivity type base region is formed in a surficial portion of the substrate. A second conductivity type first impurity region is formed in a surficial portion of the base region so as to form a pn junction with the base region. A second conductivity type second impurity region is formed in a surficial portion of the base region in a manner spaced apart from the first impurity region so as to form a pn junction with the base region. A first electrode is arranged at the surface of the substrate. A second electrode is arranged at the surface of the substrate. A dimension of the base region along the surface of the substrate between the first impurity region and the second impurity region is equal to or greater than 4.0 μm and equal to or smaller than 12.5 μm.