Redistribution Structure Trenches for Underfill CTE Stress Relief

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Solution Overview

Problem

The challenge in semiconductor packaging is the high stress generated by the coefficient of thermal expansion (CTE) mismatch between underfill and semiconductor devices, particularly in high-stress areas around the edges and gaps, which can damage the devices.

Innovation Solution

The introduction of trenches in the redistribution structure to reduce the contact area of the underfill with the semiconductor devices, combined with underfill protrusions that extend into the redistribution structure, mitigates the stress caused by CTE mismatch.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If underfill is used to fill gaps between semiconductor devices, then device stability is improved, but stress generated by CTE mismatch increases and can damage devices

Engineering Contradiction:

Improvedevice stabilityVSAvoidstress from CTE mismatch

Core Design Contradiction:

Stability of the object's compositionVSStress or pressure

Solution Approach 1:

The underfill material is segmented into multiple discrete beads rather than a continuous layer. Each bead is positioned in specific gaps between semiconductor devices, creating localized support zones that reduce overall stress while maintaining device stability. The segmentation allows stress distribution across multiple isolated points rather than continuous contact.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The underfill beads are selectively placed only in specific gaps where needed, rather than uniformly filling all spaces. This local application provides stability precisely where required while minimizing unnecessary stress generation in other areas. The local quality approach optimizes the balance between support and stress reduction.

Inventive Principle:

Principle #3Local quality

2Strength

If underfill contact area with semiconductor device is increased, then device support is improved, but stress from CTE mismatch increases

Engineering Contradiction:

Improvedevice supportVSAvoidstress from CTE mismatch

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The continuous underfill layer is divided into discrete beads, creating multiple small contact points instead of one large contact area. This segmentation maintains adequate support through distributed contact while significantly reducing the total stress transmitted to the semiconductor device from CTE mismatch.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of completely filling all gaps with underfill material, the invention uses partial filling with discrete beads. This partial action provides sufficient support for device stability while avoiding excessive contact that would generate harmful stress, achieving the optimal balance between support and stress reduction.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS20260026394A1Package and Method for Forming the Same

Publication Date: 2026.01.22 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

In an embodiment, a package including: a redistribution structure including a first dielectric layer and a first conductive element disposed in the first dielectric layer; a first semiconductor device bonded to the redistribution structure, wherein the first semiconductor device includes a first corner; and an underfill disposed over the redistribution structure and including a first protrusion extending into the first dielectric layer of the redistribution structure, wherein the first protrusion of the underfill overlaps the first corner of the first semiconductor device in a plan view.