Graded Body Contact Layout for ESD Protection Device Uniform Triggering
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Solution Overview
Problem
In electrostatic discharge (ESD) protection devices, ensuring that all fingers of a Grounded Gate n-type Metal Oxide Semiconductor Transistor (GGNMOST) trigger during an ESD event is challenging, particularly in designs where fingers share a single body contact, leading to uneven current distribution and potential device failure due to high current density and temperature.
Innovation Solution
The ESD protection device features a graded layout of body contact regions, with more or larger body contact regions located towards the periphery than the central part of the device area, encouraging triggering in the central part and reducing the likelihood of premature triggering at the ends of fingers, thereby enhancing device robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fingers share a single ring-shaped body contact, then device complexity is reduced, but current distribution becomes uneven leading to high current density in individual fingers
Solution Approach 1:
The single ring-shaped body contact is segmented into multiple discrete body contact regions distributed across the device area. This segmentation allows each finger to have its own dedicated body contact region, ensuring uniform current distribution across all fingers during ESD events while maintaining manageable device complexity through systematic arrangement of the segmented contacts.
Solution Approach 2:
Different body contact regions are strategically positioned with specific spacing and sizing characteristics tailored to local requirements. Body contact regions are placed closer to finger locations where current density needs control, while maintaining appropriate spacing in other areas. This local optimization ensures uniform current distribution without requiring a completely different overall structure.
2Reliability
If drain ballast resistance is increased to ensure all fingers trigger, then triggering reliability is improved, but voltage drop during ESD event increases
Solution Approach 1:
Body contact regions are pre-positioned and sized to create appropriate potential distribution across the substrate before the ESD event occurs. This preliminary arrangement of body contacts ensures that during an ESD event, all fingers reach their trigger voltage simultaneously without requiring excessive drain ballast resistance, thereby maintaining lower voltage drops while achieving reliable uniform triggering.
Solution Approach 2:
Multiple body contact regions are distributed across the device area, effectively copying the body contact function to multiple locations rather than relying on a single centralized contact or high resistance. This distributed copying approach ensures uniform potential distribution and simultaneous finger triggering with lower overall voltage drop.
Data Source
AI summary
An electrostatic discharge protection device and a method of making the same. The device includes a device area located on a semiconductor substrate. The device also includes an array of coextensive, laterally spaced fingers located within the device area. Each finger includes an elongate source and an elongate drain separated by an elongate gate. The fingers are electrically connected in parallel for conducting an electrostatic discharge current during an electrostatic discharge event. The device further includes a plurality of body contact regions. A layout of the body contact regions is graded such that a greater number of the body contact regions, larger body contact regions, or both are located towards a periphery of the device area than towards a central part of the device area. The layout of the body contact regions may encourage triggering of the electrostatic discharge protection device within the central part of the device area.