Back-to-Back Diode ESD Protection During BEOL Interconnection

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Solution Overview

Problem

During integrated circuit (IC) fabrication, static electrical charge can accumulate in electrical isolation regions, leading to potential electrostatic discharge (ESD) events that can damage devices or sub-circuits when they are interconnected during back end-of-line (BEOL) processing, as the IC is not yet connected to a power supply.

Innovation Solution

An electrostatic discharge (ESD) protection sub-circuit, such as a back-to-back (B2B) diode circuit, is formed in a separate electrical isolation region during front end-of-line (FEOL) processing and connected between power supply terminals of the same polarity during BEOL processing, ensuring static charge is dissipated before interconnection of devices or sub-circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If devices or sub-circuits in different electrical isolation regions are interconnected during BEOL processing, then circuit functionality is achieved, but electrostatic discharge can occur causing device damage

Engineering Contradiction:

Improvecircuit interconnectionVSAvoidelectrostatic discharge damage

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

An ESD protection sub-circuit is formed in a separate electrical isolation region during FEOL processing, before the devices or sub-circuits in different isolation regions are interconnected during BEOL processing. This preliminary formation of the protection circuit ensures that ESD protection is in place before interconnection occurs, preventing static charge buildup from causing damage when regions are connected.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The ESD protection sub-circuit acts as an intermediary element between the devices or sub-circuits in different electrical isolation regions. It provides a controlled path for electrostatic discharge, mediating the interaction between isolated regions and preventing direct harmful discharge through the devices themselves.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If ESD protection sub-circuit is formed during FEOL processing, then device protection is ensured, but fabrication process complexity increases

Engineering Contradiction:

Improvedevice protectionVSAvoidfabrication process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The ESD protection sub-circuit is formed in a separate electrical isolation region, segmented from the main device or sub-circuit regions. This segmentation allows the protection circuit to be fabricated independently during FEOL processing using the same isolation regions already created for device separation, thereby adding protection functionality without significantly increasing overall fabrication process complexity.

Inventive Principle:

Principle #1Segmentation

3Reliability

If ESD protection sub-circuit is connected between power supply terminals during BEOL processing, then static charge dissipation is enabled, but additional interconnection layers are required

Engineering Contradiction:

Improvestatic charge dissipationVSAvoidinterconnection structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The power supply terminal interconnection structure is made multi-functional by using it for both its primary purpose (power supply connection) and the secondary purpose of connecting the ESD protection sub-circuit. The same power supply terminal network serves dual functions: delivering power to devices and providing a connection path for the ESD protection circuit, thereby enabling static charge dissipation without requiring separate dedicated interconnection layers.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 prevents damage from ESD events by controlling the discharge through the B2B diodes, maintaining device integrity and functionality without adversely affecting the IC's performance or adding significant processing time.

Implementation Method 1

static electrical charge will be controllably dissipated by the ESD protection sub-circuit

Methodology Applied

Scientific EffectElectrostatic discharge: Electrostatic Discharge

Data Source

PatentUS20250324767A1Electrostatic discharge protection for integrated circuit during back end-of-line processing

Publication Date: 2025.10.16 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.