Back-to-Back Diode ESD Protection During BEOL Interconnection

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Solution Overview

Problem

During integrated circuit (IC) fabrication, electrical isolation regions can trap static electrical charge, leading to potential electrostatic discharge (ESD) events when interconnected, which may damage devices or sub-circuits, as they are not yet connected to a power supply and lack adequate charge dissipation pathways.

Innovation Solution

An electrostatic discharge (ESD) protection sub-circuit, comprising back-to-back diodes, is formed in a separate electrical isolation region and connected between power supply terminals before the main devices or sub-circuits are interconnected, allowing for controlled dissipation of static charge during the metallization stage of IC fabrication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electrical isolation regions are interconnected during metallization stage, then device functionality is achieved, but electrostatic discharge damage occurs due to trapped static charge

Engineering Contradiction:

Improvedevice integrityVSAvoidelectrostatic discharge

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

ESD protection sub-circuits are formed and connected to power supply terminals during front end-of-line processing, before the metallization stage interconnections are made. This preliminary establishment of protection pathways ensures that when isolation regions are later interconnected, static charge can be safely dissipated through the pre-positioned ESD protection circuits rather than damaging sensitive devices

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

ESD protection sub-circuits act as intermediary elements between electrical isolation regions that may have trapped static charge. These protection circuits provide a controlled pathway for charge dissipation, mediating the interaction between isolated regions during interconnection and preventing direct ESD events that would occur without such intermediary protection structures

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If ESD protection sub-circuit is formed in separate electrical isolation region, then charge dissipation pathway is provided, but fabrication process complexity increases

Engineering Contradiction:

ImproveESD protectionVSAvoidfabrication process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The formation of ESD protection sub-circuits is merged with existing front end-of-line processing steps. By integrating ESD protection circuit formation into the standard fabrication sequence already in place for creating devices and interconnects, the process adds protection functionality without requiring separate dedicated fabrication stages, thus limiting the increase in overall process complexity

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

This solution effectively prevents damage from electrostatic discharge by ensuring static charge is dissipated before connections are made, maintaining the integrity of the IC components during the fabrication process without impacting the final IC performance.

Implementation Method 1

electrostatic discharge (ESD) protection arts, and to related arts... preventing damage from electrostatic discharge by ensuring static charge is dissipated

Methodology Applied

Scientific EffectElectrostatic discharge: Electrostatic Discharge

Data Source

PatentUS11764206B2Electrostatic discharge protection for integrated circuit during back end-of-line processing

Publication Date: 2023.09.19 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

In an integrated circuit (IC) fabrication process, devices or sub-circuits are fabricated in respective first and second electrical isolation regions. A back-to-back (B2B) diodes sub-circuit is fabricated in a third electrical isolation region, which includes a first diode whose cathode is connected with a first terminal and whose anode is connected with a second terminal, and a second diode whose anode is connected with the first terminal and whose cathode is connected with the second terminal. Electrostatic discharge protection is provided to the first and second electrical isolation regions by electrically connecting the first terminal of the B2B diodes sub-circuit with a VSS power supply terminal of the first device or sub-circuit and the second terminal of the B2B diodes sub-circuit with a VSS power supply terminal of the second device or sub-circuit. Thereafter, the first device or sub-circuit and the second device or sub-circuit are electrically connected.