Two-Region Base TVS Device for Breakdown Voltage and Resistance Trade-off
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Solution Overview
Problem
Existing transient voltage suppressor (TVS) devices with uniformly doped bases face limitations in achieving high breakdown voltage and low electric field requirements, leading to thick base regions that complicate fabrication and increase resistance, especially at high voltages, necessitating deep etch processes and special mask protection.
Innovation Solution
A TVS device design featuring a base region with two layers of different doping concentrations and thicknesses, allowing independent control of breakdown voltage and electric field, enabling a thinner base structure without sacrificing performance and simplifying the fabrication process by eliminating the need for edge termination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base thickness is increased to achieve higher breakdown voltage, then the breakdown voltage capability is improved, but the device resistance increases and clamping capability deteriorates
Solution Approach 1:
The base region is divided into two zones with different doping concentrations: a first zone with lower doping concentration to support high breakdown voltage, and a second zone with higher doping concentration to reduce resistance. This local differentiation allows each zone to optimize for its specific function, resolving the contradiction between high breakdown voltage capability and low device resistance.
2Reliability
If the base thickness is increased to maintain low electric field, then the electric field is reduced, but the fabrication complexity increases due to deep etch processes
Solution Approach 1:
Instead of uniformly increasing base thickness to control electric field, the invention changes the doping concentration parameter across different zones. The higher doping concentration in the second zone allows for a thinner overall base structure while maintaining electric field control, thereby avoiding deep etch processes and reducing fabrication complexity.
3Reliability
If the base thickness is increased to achieve higher breakdown voltage, then the breakdown voltage is improved, but the fabrication cost increases due to special mask protection requirements
Solution Approach 1:
The differentiated doping zones enable selective optimization: the first zone provides high breakdown voltage with moderate thickness, while the second zone reduces the need for excessive thickness. This allows standard etch processes to be used without requiring special mask protection for deep etching, thereby reducing fabrication costs while maintaining high breakdown voltage capability.
4Reliability
If the base thickness is increased to maintain low doping concentration, then the breakdown voltage is improved, but the device resistance increases
Solution Approach 1:
The base is segmented into two zones with different doping concentrations. The first zone has lower doping concentration to enable high breakdown voltage, while the second zone has higher doping concentration to reduce device resistance. This spatial differentiation of doping levels allows both requirements to be satisfied simultaneously without compromise.
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 two-layer base design reduces the base thickness while maintaining breakdown voltage and electric field requirements, simplifying the etch process, minimizing leakage current, and lowering fabrication costs by allowing electric field confinement within the bulk region, thus enhancing circuit protection capabilities.
Implementation Method 1
The TVS device reaches breakdown when a depletion region of a reverse biased p-n junction reaches another p-n junction depletion region
Implementation Method 2
The blocking capability of the TVS device is defined by its base thickness and doping
Implementation Method 3
Punch-through limited breakdown design allows a simplification of the structure
Implementation Method 4
a second layer of wide band-gap semiconductor material formed of a second conductivity type material over at least a portion of the first layer, the second layer including a first concentration of dopant
Data Source
AI summary
A transient voltage suppression (TVS) device and a method of forming the device are provided. The TVS device includes a first layer of wide band-gap semiconductor material formed of a first conductivity type material, a second layer of wide band-gap semiconductor material formed of a second conductivity type material over at least a portion of the first layer, the second layer including a first concentration of dopant. The TVS device further including a third layer of wide band-gap semiconductor material formed of the second conductivity type material over at least a portion of the second layer, the third layer including a second concentration of dopant, the second concentration of dopant being different than the first concentration of dopant. The TVS device further including a fourth layer of wide band-gap semiconductor material formed of the first conductivity type material over at least a portion of the third layer.