Post-Passivation Interconnect Adhesion via Polymer Roughness

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Solution Overview

Problem

The existing Post-Passivation Interconnect (PPI) structure in integrated circuit manufacturing faces issues with delamination at the interfaces between the polymer layer and the PPI due to differences in thermal expansion and contraction during the reflow process, leading to reliability concerns.

Innovation Solution

A surface treatment is performed on the polymer layer to increase its roughness, enhancing adhesion between the polymer layer and the PPI, which involves sputtering to create a rougher surface, thereby improving the bonding and reducing delamination risks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a smooth polymer layer is used over the PPI, then the manufacturing process is simpler, but delamination occurs during reflow due to thermal expansion differences

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidadhesion between polymer layer and PPI

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The surface roughness of the polymer layer is changed from smooth to rough through controlled oxidation or plasma treatment. This parameter change increases the surface area and creates mechanical interlocking features that enhance adhesion between the polymer layer and the underlying PPI structure, preventing delamination during thermal reflow processes.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The smooth surface interface is replaced with a chemically treated surface that creates stronger bonding. Oxidation or plasma treatment introduces reactive groups on the polymer surface that form chemical bonds with the PPI, substituting the weak van der Waals forces of a smooth interface with stronger chemical adhesion mechanisms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If the polymer layer surface is treated to increase roughness, then adhesion is improved, but the process complexity increases

Engineering Contradiction:

Improveadhesion between polymer layer and PPIVSAvoidprocess complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The surface treatment (oxidation or plasma) is performed as a preliminary step before final assembly or testing. By preparing the polymer layer surface in advance with enhanced adhesion properties, the subsequent reflow process proceeds without delamination issues, and the treatment itself can be integrated into existing manufacturing workflows with minimal additional complexity.

Inventive Principle:

Principle #10Preliminary 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 surface treatment significantly improves the adhesion between the polymer layer and the PPI, preventing delamination and ensuring the structural integrity of the PPI during high-temperature reflow processes.

Implementation Method 1

A surface treatment is performed on the polymer layer to increase its roughness, enhancing adhesion between the polymer layer and the PPI, which involves sputtering to create a rougher surface

Methodology Applied

Scientific EffectSputtering: Sputtering

Data Source

PatentUS8846548B2Post-passivation interconnect structure and methods for forming the same

Publication Date: 2014.09.30 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method includes forming a polymer layer over a passivation layer, wherein the passivation layer further comprises a portion over a metal pad. The polymer layer is patterned to form an opening in the polymer layer, wherein exposed surfaces of the polymer layer have a first roughness. A surface treatment is performed to increase a roughness of the polymer layer to a second roughness greater than the first roughness. A metallic feature is formed over the exposed surface of the polymer layer.