Symmetrical Bipolar ESD Structure for Bi-Directional High-Voltage Protection

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Solution Overview

Problem

Conventional ESD protection devices are unidirectional and cannot effectively handle bi-directional high voltage biases, leading to inadequate protection against electrostatic discharge (ESD) in electronic apparatuses.

Innovation Solution

A bi-directional ESD protection device is designed with a symmetrical bi-polar transistor structure, including highly doped terminal regions, a floating center island region, and an insulating layer, allowing for bi-directional current conduction and improved ESD protection by isolating the floating region from terminal regions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a normal unidirectional bi-polar ESD protection device is used, then it can protect against ESD in one direction, but it cannot provide protection when voltage bias is applied in the opposite direction

Engineering Contradiction:

Improvebi-directional protection capabilityVSAvoidprotection reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The device is segmented into two symmetrical bi-polar transistor structures (first NPN transistor and second NPN transistor) that operate in opposite directions. Each transistor handles one polarity of voltage bias independently, allowing the device to provide protection in both directions without interference between polarities

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

While the overall structure is symmetrical to enable bi-directional operation, each individual transistor structure is asymmetric in its doping configuration (emitter, base, collector regions with different doping concentrations). This asymmetric doping within each transistor enables effective ESD protection while the symmetric arrangement of two such transistors provides bi-directional capability

Inventive Principle:

Principle #4Asymmetry

2Reliability

If the doping concentration of terminal regions is increased to reduce on-resistance, then ESD protection effectiveness improves, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

ImproveESD protection effectivenessVSAvoiddoping structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Different doping concentrations are applied to different regions: the emitter and collector terminal regions have high doping concentrations (1E19 to 1E21 atoms/cm³) to reduce on-resistance and improve ESD protection, while the base region has lower doping concentration (1E16 to 1E18 atoms/cm³) to maintain transistor functionality. This localized variation in doping quality optimizes performance without uniformly increasing complexity throughout the device

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If a symmetrical bi-polar transistor structure is used to achieve bi-directional operation, then protection in both directions is enabled, but the device footprint increases

Engineering Contradiction:

Improvebi-directional operation capabilityVSAvoiddevice footprint

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

Two bi-polar transistor structures are merged into a single integrated device with shared substrate and interconnected terminals. The first and second NPN transistors are combined in one device package, allowing bi-directional protection functionality to be achieved without requiring two separate devices, thereby minimizing the overall footprint while maintaining full bi-directional capability

Inventive Principle:

Principle #5Merging (Combining)

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 bi-directional ESD protection device effectively conducts current away from apparatuses during high ESD voltages, providing enhanced protection with a compact footprint and high holding voltage, thus preventing latch-up and minimizing on-resistance.

Implementation Method 1

the ESD protection device may turn on to conduct current away from the apparatus, hence protecting the apparatus from damage

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

an insulating layer arranged on the substrate between the first and second conductive terminals, the insulating layer covering at least the second doped region

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Data Source

PatentUS11862735B2Bi-directional bi-polar device for ESD protection

Publication Date: 2024.01.02 GLOBALFOUNDRIES SINGAPORE PTE LTD

AI summary

An electrostatic discharge (ESD) protection device including: a substrate including: a first, second and third doped regions, the second doped region disposed between the first and third doped regions, the second doped region has a first conductivity type and a first doping concentration and the first and third doped regions have a second conductivity type and a second doping concentration; first and second doped terminal regions disposed within the first and second doped regions, respectively; and a doped island region disposed within the second doped region, the first and second doped terminal regions and doped island region have the second conductivity type and a third doping concentration, the third doping concentration higher than the first and second doping concentrations; and conductive terminals respectively coupled to the doped terminal regions; and an insulation layer arranged on the substrate between the conductive terminals and covering at least the second doped region.