Patterned Buffer Layer for Flip-Chip Delamination Prevention

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Solution Overview

Problem

Delamination issues between the underfill and polyimide layer in flip-chip bond structures occur due to stress-related warpage, affecting the reliability of the bond structure.

Innovation Solution

A patterned buffer layer is introduced, formed from softer and more elastic materials than the passivation layer, which is patterned using lithography masks to create discrete portions that prevent lateral growth of delamination and enhance adhesion between the underfill and underlying layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If underfill is filled between chip and package substrate to protect solder bumps, then solder bump protection is improved, but delamination occurs between underfill and polyimide layer due to stress-induced warpage

Engineering Contradiction:

Improvesolder bump protectionVSAvoidadhesion between underfill and polyimide layer

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The buffer layer is segmented into discrete patterned portions rather than a continuous layer. This segmentation prevents stress from propagating continuously across the interface, thereby preventing delamination while still providing protection to solder bumps through the distributed buffer portions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The buffer layer is made softer and more elastic locally at the interface between underfill and polyimide layer. This local change in material properties allows the buffer layer to absorb stress and prevent warpage-induced delamination, while maintaining solder bump protection.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If a continuous buffer layer is used to prevent delamination, then adhesion is improved, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improveadhesion between underfill and polyimide layerVSAvoidbuffer layer structure

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The buffer layer is divided into discrete patterned portions that are simpler to manufacture than a continuous layer. The patterned structure can be formed using standard lithography techniques, reducing manufacturing complexity while still providing effective stress management and delamination prevention.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using a full continuous buffer layer, discrete patterned portions are sufficient to prevent delamination. This partial action approach reduces the amount of material and processing required, simplifying the device structure and manufacturing process.

Inventive Principle:

Principle #16Partial or excessive action

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 patterned buffer layer effectively prevents delamination between the underfill and polyimide layer, improving the reliability and adhesion of the bond structure, thereby enhancing the structural integrity of the flip-chip package.

Implementation Method 1

A patterned buffer layer is introduced, formed from softer and more elastic materials than the passivation layer

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

The delamination is caused due to process issues such as the warpage resulted from the high stress near the interface between underfill 216 and polyimide layer 220

Methodology Applied

Scientific EffectStress relaxation: Stress Relaxation

Implementation Method 3

which is patterned using lithography masks to create discrete portions

Methodology Applied

Scientific EffectPhotolithography: Photography

Data Source

PatentUS8963328B2Reducing delamination between an underfill and a buffer layer in a bond structure

Publication Date: 2015.02.24 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A die includes a metal pad, a passivation layer, and a patterned buffer layer over the passivation layer. The patterned buffer layer includes a plurality of discrete portions separated from each other. An under-bump-metallurgy (UBM) is formed in an opening in the patterned buffer layer and an opening in the passivation layer. A metal bump is formed over and electrically coupled to the UBM.