Multi-channel ESD Finger Homogeneous Triggering via Distributed Base
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Solution Overview
Problem
Current ESD protection circuits for high voltage MOS devices are inadequate in handling enhanced high energy electrostatic discharge (ESD) without damaging the integrated circuit, particularly due to non-uniform finger triggering and high current peaks during ESD events, which can lead to reduced robustness and efficiency in protecting the devices.
Innovation Solution
The proposed solution involves a novel ESD protection apparatus with multiple ESD fingers connected to a distributed base connection, polysilicon gate, and ground connection, featuring NMOS and NPN bipolar devices with specific resistor configurations to ensure simultaneous triggering and homogeneous current sharing among the fingers, thereby enhancing mutual triggering and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple ESD fingers are used to handle high energy ESD discharge, then the ESD protection capability is improved, but the fingers trigger non-uniformly leading to reduced efficiency
Solution Approach 1:
The patent applies equipotentiality by connecting all ESD finger bases to a common distributed base connection, ensuring that all fingers experience the same base potential during ESD events. This equalizes the triggering conditions across all fingers, causing them to snapback simultaneously and utilize the full ESD energy, thereby resolving the non-uniform triggering problem while maintaining high ESD protection capability.
Solution Approach 2:
The patent segments the ESD protection function into multiple parallel ESD fingers, each capable of handling a portion of the ESD current. By distributing the protection function across multiple fingers with shared base connections, the system achieves both high ESD capability and uniform triggering through the common base potential.
2Reliability
If a 220 pF load capacitor is added for automotive protection, then the protection coverage is improved, but the current peak is significantly amplified causing potential damage
Solution Approach 1:
The patent segments the ESD protection function into multiple parallel ESD fingers that share the total ESD current. By distributing the current handling across multiple fingers with a common base connection, the peak current is divided and managed more effectively, reducing the harmful current peak while maintaining comprehensive protection coverage through the 220 pF capacitor.
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 significantly improves the robustness of ESD protection by ensuring all ESD fingers trigger simultaneously, leading to increased efficiency and a 50% enhancement in ESD capability, effectively handling high energy discharges and meeting stringent automotive industry requirements.
Implementation Method 1
High energy ESD discharge (8KV HBM / 6KV IEC 61000.4) induces high current peak flowing in the ESD protection
Implementation Method 2
Adding a 220 pF load capacitor in parallel with the integrated circuit device signal pad for protection
Data Source
Figure 1
Figure 2~3
Figure 4A
AI summary
Mutual triggering of electrostatic discharge (ESD) fingers is improved by creating a base contact in each individual finger and connecting all of these base contacts in parallel. The local base contact in each ESD finger is located at a position where the base voltage significantly increases when the ESD current increases. Thus when an ESD finger is triggered its local base voltage will tend to significantly increase. Since all of the ESD finger bases are connected in parallel this local voltage increase will forward bias die base-emitter junctions of the other ESD fingers, thus triggering them all. By sharing the triggering current from the fastest ESD finger with the slower ones ensures that all ESD fingers are triggered during an ESD event.