Bidirectional ESD Protection Layout for Lower Clamping Voltage
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Solution Overview
Problem
Conventional bidirectional ESD protection devices face challenges with high clamping voltage in the discharging path and increased fabrication complexity due to the use of multiple diodes and ESD elements, which affect the reliability of CMOS IC products in nanoscale processes.
Innovation Solution
A bidirectional ESD protection device is designed with two transient voltage suppressor chips, each comprising a diode and a PNP or NPN bipolar junction transistor, connected by conductive wires to reduce parasitic capacitance and clamping voltage, while using fewer ESD elements in series to decrease fabrication complexity and enhance ESD levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three ESD elements are connected in series in the discharging path, then the ESD protection device can provide a low resistance path for discharging, but the clamping voltage becomes higher
Solution Approach 1:
The patent divides the ESD protection device into two separate transient voltage suppressor chips, with each chip containing a diode and a PNP bipolar junction transistor. This segmentation allows the discharging path and reverse breakdown path to be independently optimized, enabling lower clamping voltage in the discharging path while maintaining adequate breakdown voltage in the reverse breakdown path through separate component configurations.
2Reliability
If a buried layer is used to connect diodes, then the ESD paths can be formed, but the fabrication complexity increases
Solution Approach 1:
The patent extracts the PNP bipolar junction transistor from the conventional diode-only structure and introduces it into the ESD protection circuit. This extraction allows the formation of ESD paths through the transistor's collector-emitter junction, eliminating the need for complex buried layer connections while maintaining reliable ESD path connectivity through the transistor's inherent conductive properties.
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 solution achieves a lower clamping voltage in the discharging path and improved ESD levels by using two ESD elements in the reverse breakdown path, increasing the breakdown voltage and reducing fabrication complexity through the use of conductive wires and inductors.
Implementation Method 1
The bidirectional ESD protection device uses two ESD elements to sustain a reverse voltage in a reverse breakdown path, such that the breakdown voltage of the ESD elements easily exceeds the total turned-on voltage applied to a discharging path
Implementation Method 2
connected by conductive wires to reduce parasitic capacitance and clamping voltage
Data Source
AI summary
A bidirectional electrostatic discharge protection device includes a first transient voltage suppressor chip, a second transient voltage suppressor chip, a first conductive wire, and a second conductive wire. The first transient voltage suppressor chip includes a first diode and a first bipolar junction transistor. The first diode and the first bipolar junction transistor are electrically connected to a first pin. The second transient voltage suppressor chip includes a second diode and a second bipolar junction transistor. The second diode and the second bipolar junction transistor are electrically connected to a second pin. The first conductive wire is electrically connected between the first diode and the second bipolar junction transistor. The second conductive wire is electrically connected between the second diode and the first bipolar junction transistor.