IC Bonding Pad Capping for Wet-Clean Corrosion Protection

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Solution Overview

Problem

In the formation of three-dimensional (3D) packages, existing bonding technologies face challenges in preventing galvanic corrosion of metal pads during the bonding process, which can damage the integrity of the diffusion barrier and affect the reliability of the bond.

Innovation Solution

The formation of a capping layer over the metal pad, followed by a wet pre-cleaning process and optional sputtering to remove the exposed portion of the capping layer, prevents galvanic corrosion by protecting the metal pad from chemical exposure and ensures the integrity of the diffusion barrier.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a wet pre-cleaning process is performed to clean the bonding structure, then cleaning effectiveness is improved, but galvanic corrosion of the metal pad occurs due to chemical exposure

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidgalvanic corrosion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A capping layer is introduced as an intermediary protective barrier between the metal pad and the chemical solution during wet pre-cleaning. The capping layer allows the cleaning process to proceed effectively while preventing direct chemical exposure to the metal pad, thereby eliminating galvanic corrosion risk

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The capping layer is formed over the metal pad before the wet pre-cleaning process is performed. This preliminary protective action ensures that when the chemical solution is applied during cleaning, the metal pad is already shielded and cannot undergo galvanic corrosion

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If the capping layer is removed by sputtering to expose the metal pad, then direct metal-to-metal bonding is enabled, but the diffusion barrier may be damaged

Engineering Contradiction:

Improvebonding capabilityVSAvoiddiffusion barrier integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The capping layer serves as a protective intermediary that is selectively removed only in the bonding region through sputtering. This controlled removal enables direct metal-to-metal bonding while the remaining capping layer continues to protect other metal pads from chemical exposure and diffusion barrier damage

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively prevents galvanic corrosion of the metal pads, maintaining the integrity of the diffusion barrier and ensuring reliable bonding in 3D packages by using a capping layer to shield the metal pads from chemical exposure during the bonding process.

Implementation Method 1

forming a capping layer over the metal pad... prevents galvanic corrosion by protecting the metal pad from chemical exposure

Methodology Applied

Scientific EffectPhysical barrier protection:

Implementation Method 2

optional sputtering to remove the exposed portion of the capping layer

Methodology Applied

Scientific EffectSputtering: Sputtering

Data Source

PatentUS11990430B2Bonding structures of integrated circuit devices and method forming the same

Publication Date: 2024.05.21 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method includes forming a conductive pad over an interconnect structure of a wafer, forming a capping layer over the conductive pad, forming a dielectric layer covering the capping layer, and etching the dielectric layer to form an opening in the dielectric layer. The capping layer is exposed to the opening. A wet-cleaning process is then performed on the wafer. During the wet-cleaning process, a top surface of the capping layer is exposed to a chemical solution used for performing the wet-cleaning process. The method further includes depositing a conductive diffusion barrier extending into the opening, and depositing a conductive material over the conductive diffusion barrier.