Cu Pillar Bump Non-Metal Sidewall Spacer Metal Top Cap

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Solution Overview

Problem

Copper pillar bump technology faces issues such as oxidation during manufacturing, leading to poor adhesion and reliability concerns, along with defects in the formation of metal layer caps and photoresist residue, which affect the performance and reliability of integrated circuit packaging.

Innovation Solution

The formation of a sidewall spacer using non-metal material layers and a top cap through electroless or immersion metal deposition processes, such as ENEPIG, ENEP, EN, or ENIG structures, to prevent copper oxidation and improve adhesion and reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an immersion tin process is employed to provide a tin layer on the Cu pillar sidewalls, then copper oxidation is prevented, but process costs increase and adhesion between Sn and underfill deteriorates

Engineering Contradiction:

Improvecopper oxidation preventionVSAvoidprocess cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the material parameter from tin (Sn) to non-metallic materials such as silicon oxide, silicon nitride, or organic dielectric materials. This parameter change eliminates the adhesion problems between Sn and underfill while maintaining oxidation protection, and reduces process costs by using more compatible materials with existing semiconductor fabrication processes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite structures combining multiple non-metallic layers (e.g., silicon oxide and silicon nitride) to provide both oxidation protection and mechanical stability. This composite approach eliminates the need for tin layers while maintaining or improving overall structure reliability and adhesion properties

Inventive Principle:

Principle #40Composite materials

2Reliability

If a metal layer cap is formed using electroless/immersion metal deposition process, then copper oxidation is prevented, but photoresist leaching and delamination occur

Engineering Contradiction:

Improvecopper oxidation preventionVSAvoidphotoresist integrity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent introduces non-metallic sidewall spacer layers as intermediary structures between the copper pillar and the bonding interface. These spacers serve as both oxidation barriers and mechanical support structures, eliminating the need for metal caps that cause photoresist leaching while maintaining copper protection

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent extracts the oxidation protection function from the metal cap structure and relocates it to non-metallic sidewall spacer layers. This separation eliminates the harmful interaction between immersion metals and photoresist while preserving the essential oxidation prevention capability

Inventive Principle:

Principle #2Taking out (Extraction)

3Manufacturing precision

If copper pillar bumps are used to achieve finer pitch, then bump bridging probability is reduced, but copper oxidation leads to poor adhesion

Engineering Contradiction:

Improvepitch precisionVSAvoidadhesion quality

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent creates a composite structure with non-metallic sidewall spacers surrounding the copper pillar. This composite design maintains the fine pitch advantages of copper pillars while the non-metallic spacers provide oxidation protection and improve adhesion to underfill materials, preventing the reliability issues associated with oxidized copper surfaces

Inventive Principle:

Principle #40Composite materials

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 effectively prevents copper oxidation, enhances adhesion, reduces defects, and improves the reliability of copper pillar bumps by using non-metal sidewall spacers and metal top caps, addressing the challenges of photoresist leaching and residue issues while maintaining fine pitch package compatibility.

Implementation Method 1

a sidewall spacer, serving as a protection structure on the sidewalls of the Cu pillar bump, is formed by having at least one of several non-metal material layers

Methodology Applied

Scientific EffectOxidation prevention: Physical Containment

Implementation Method 2

The top cap, serving as a barrier structure on the top surface of the Cu pillar bump for preventing copper from diffusing into bonding material, includes at least one metal layer formed by electroless or immersion metal deposition process

Methodology Applied

Scientific EffectElectroless deposition: Deposition (physical)

Implementation Method 3

Methodology Applied

Scientific EffectImmersion deposition: Deposition (physical)

Data Source

PatentUS9018758B2Cu pillar bump with non-metal sidewall spacer and metal top cap

Publication Date: 2015.04.28 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A bump has a non-metal sidewall spacer on a lower sidewall portion of Cu pillar, and a metal top cap on a top surface and an upper sidewall portion of the Cu pillar. The metal top cap is formed by an electroless or immersion plating technique after the non-metal sidewall spacer formation.