Multi-Finger SPAD ESD Layout for Uniform Turn-On Stability
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Solution Overview
Problem
Conventional ESD protection devices face challenges in maintaining operational stability and uniform turn-on characteristics, particularly in high-voltage environments, leading to potential device damage and performance degradation due to non-simultaneous finger activation during ESD events.
Innovation Solution
The proposed ESD protection device incorporates a PNP-type configuration with a multi-finger structure, base moats, and external resistors to ensure uniform turn-on characteristics by connecting emitter fingers and base wells with metal, allowing all fingers to activate simultaneously and adjust triggering voltages, thereby improving operational stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of ESD protection device is reduced to match shrinking chip sizes, then device integration is improved, but ESD immunity deteriorates
Solution Approach 1:
The ESD protection device is divided into multiple emitter fingers (first, second, third emitter fingers) arranged in a multi-finger configuration. This segmentation allows the device to maintain adequate protection capability while reducing the overall footprint area, resolving the contradiction between device size reduction and ESD immunity maintenance.
Solution Approach 2:
The patent transitions from a conventional single-emitter layout to a multi-finger structure that utilizes two-dimensional spatial arrangement. The emitter fingers are positioned at different locations with specific spacing, effectively using planar dimensionality to reduce the concentrated area while maintaining protection effectiveness through distributed geometry.
2Ease of manufacture
If conventional ESD protection device layout is used, then manufacturing is simplified, but turn-on characteristics become non-uniform leading to operational instability
Solution Approach 1:
The patent introduces a base moat structure that electrically connects the bases of all emitter fingers, establishing equipotential conditions across the device. This ensures uniform voltage distribution and simultaneous turn-on characteristics of all emitter fingers, resolving the operational instability caused by non-uniform turn-on while maintaining layout simplicity through the shared base connection architecture.
3Area of stationary object
If emitter fingers are spaced closer to reduce area, then device area is reduced, but current distribution becomes non-uniform
Solution Approach 1:
The base moat structure creates an equipotential region that connects all emitter finger bases, ensuring uniform voltage distribution across closely spaced emitter fingers. This equipotential connection compensates for the reduced spacing between emitter fingers, maintaining uniform current distribution while achieving compact device area.
Solution Approach 2:
The patent applies different doping concentrations to different regions: high concentration in the base moat for low resistance connection, and optimized concentrations in emitter and collector regions. This local quality differentiation ensures uniform current distribution across closely spaced emitter fingers while maintaining compact overall device area.
Data Source
AI summary
Disclosed are an ESD protection device to mitigate performance degradation due to operational instability by ensuring protection against ESD events and stress. The ESD protection device includes an N-type buried layer including a first dopant type in a semiconductor substrate, a deep well (DNW) including a first dopant type on the N-type buried layer, a first doped region including a first dopant type on the deep well, a second doped region including a first dopant type and a third doped region including a second dopant type, spaced apart from the first doped region, a base in the first doped region, and a multi-finger structure including emitter fingers in the second doped region and collector fingers in the third doped region, and a base moat comprising a base metal connecting individual ones of the emitter fingers to each other.