Vertical TVS Circuit with Trench Gate Isolation
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Solution Overview
Problem
Existing transient voltage suppressor (TVS) circuits face challenges with high diode series resistance due to substrate resistivity, leading to increased junction capacitance and poor clamping performance, which limits miniaturization and increases the size of devices intended for protecting integrated circuits from overvoltage events.
Innovation Solution
The implementation of DMOS technology with trench gate structures as part of the TVS structure, functioning as channel isolation and filter capacitors, to achieve a compact silicon die footprint and enhance integrated circuit cell density, thereby reducing production costs and improving clamping performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional substrate-based TVS diodes are used, then the device structure is simple, but the substrate resistivity causes high diode series resistance and increased junction capacitance
Solution Approach 1:
The patent changes the fundamental structural parameter from horizontal substrate-based diodes to vertical trench DMOS structures. This parameter change transforms the current flow path and reduces the effective resistance by utilizing the vertical channel structure, thereby improving clamping performance without significantly increasing device complexity
Solution Approach 2:
The patent transitions from a two-dimensional planar diode structure to a three-dimensional vertical trench structure. By adding the vertical dimension with deep trenches extending into the substrate, the device achieves lower series resistance and reduced junction capacitance while maintaining a compact footprint
2Reliability
If larger diode size is used to reduce resistance, then the diode resistance decreases, but the device area increases limiting miniaturization
Solution Approach 1:
The patent resolves this contradiction by moving from lateral current flow in planar diodes to vertical current flow in trench structures. The vertical orientation allows the current to travel through the depth of the trench rather than across the surface area, enabling low resistance with minimal footprint
Solution Approach 2:
The patent embeds the TVS function within the vertical trench structure, nesting the protective function inside the DMOS device architecture. This nested configuration allows the TVS functionality to be integrated within the existing device footprint without requiring additional lateral space
3Area of moving object
If vertical trench DMOS structures are implemented, then the silicon die footprint is reduced and cell density increases, but the manufacturing process complexity increases
Solution Approach 1:
The patent makes the trench structure serve multiple functions: it provides channel isolation, forms the TVS protective element, and creates the DMOS device structure. This multi-functionality reduces the need for separate manufacturing steps and structures, thereby reducing overall process complexity despite the vertical architecture
Solution Approach 2:
The patent combines the isolation trench and the TVS structure into a single integrated feature. By merging these functions into one vertical structure, the patent eliminates the need for separate isolation and protective device manufacturing steps, simplifying the overall process
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
This approach results in a low-cost, high-density TVS and EMI filter circuit with improved clamping performance and reduced size, effectively addressing the limitations of traditional TVS designs by utilizing DMOS processes to integrate vertical trench structures for enhanced performance and cost-effectiveness.
Implementation Method 1
trench gate structures as part of the TVS structure, functioning as channel isolation and filter capacitors
Data Source
AI summary
A vertical TVS (VTVS) circuit includes a semiconductor substrate for supporting the VTVS device thereon having a heavily doped layer extending to the bottom of substrate. Deep trenches are provided for isolation between multi-channel VTVS. Trench gates are also provided for increasing the capacitance of VTVS with integrated EMI filter.