Plasma-Roughened UBM Pads for Reliable Polymer Interconnects

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Solution Overview

Problem

Current semiconductor packaging technologies face challenges in achieving reliable connections between underball metallization (UBM) pads and connectors due to the formation of intermetallic compounds (IMCs) at the edges, which can lead to adhesion issues and reliability problems, especially when using polymer materials.

Innovation Solution

The method involves forming connector pad structures with UBM pads that undergo a plasma treatment to increase surface roughness, preventing IMC formation between the polymer material and the UBM pads, and using a low-activity flux to facilitate connector attachment without damaging the interface, thereby enhancing adhesion and reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If connectors are attached to UBM pads using conventional methods, then electrical connections are established, but intermetallic compounds form at the edges causing adhesion issues and reliability problems

Engineering Contradiction:

Improveconnector adhesion reliabilityVSAvoidintermetallic compound formation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The UBM pad surface is roughened before connector attachment through plasma treatment or chemical etching. This preliminary surface modification creates a textured surface that prevents IMC formation at edges during subsequent reflow processing, thereby improving long-term adhesion reliability without compromising initial connection strength

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The surface roughness parameter of the UBM pad is deliberately modified from a smooth state to a roughened state with controlled Ra values. This parameter change transforms the surface morphology to prevent edge IMC formation while maintaining adequate wetting and adhesion properties for connector attachment

Inventive Principle:

Principle #35Parameter changes

2Reliability

If surface roughness is increased to prevent IMC formation, then adhesion reliability improves, but manufacturing complexity increases due to additional plasma treatment or etching steps

Engineering Contradiction:

Improveinterface adhesion reliabilityVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The surface roughening step is integrated with the existing UBM formation process by performing plasma treatment or chemical etching immediately after UBM deposition while the substrate is already in the processing chamber. This merging eliminates the need for separate surface preparation steps and reduces overall manufacturing complexity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

A flux material is introduced as an intermediary substance during connector attachment that works synergistically with the roughened surface. The flux fills in the surface irregularities and promotes uniform wetting, thereby maintaining adhesion reliability while allowing the use of simpler roughening methods

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If polymer material is used over UBM pads, then planarization and subsequent processing are facilitated, but IMC formation at edges still occurs causing delamination

Engineering Contradiction:

Improveplanarization easeVSAvoidpolymer-UBM interface reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The UBM pad surface is roughened before polymer deposition to prevent edge IMC formation that would otherwise occur during subsequent reflow or curing processes. This preliminary surface modification ensures long-term interface reliability while maintaining the planarization benefits of using polymer materials

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The surface roughening is applied selectively only to the UBM pad regions where connectors will be attached, while the surrounding polymer material remains smooth. This localized quality change prevents IMC formation at critical interface points without compromising the overall planarization and ease of manufacture

Inventive Principle:

Principle #3Local quality

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 improves the reliability of connector pad structures by preventing IMC formation between the polymer material and UBM pads, leading to robust interfaces and reduced delamination, and allows for cost-effective and high-yield ball mount processes in semiconductor packaging.

Implementation Method 1

The UBM pad is roughened by exposing the UBM pad to a plasma treatment

Methodology Applied

Scientific EffectPlasma treatment: Plasma

Data Source

PatentUS10840199B2Methods of forming connector pad structures, interconnect structures, and structures thereof

Publication Date: 2020.11.17 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Methods of forming connector pad structures, interconnect structures, and structures thereof are disclosed. In some embodiments, a method of forming a connector pad structure includes forming an underball metallization (UBM) pad, and increasing a surface roughness of the UBM pad by exposing the UBM pad to a plasma treatment. A polymer material is formed over a first portion of the UBM pad, leaving a second portion of the UBM pad exposed.