Convex Under-Bump Metal Layer for Semiconductor Terminal

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Solution Overview

Problem

Conventional bump formation methods struggle to achieve a balance between mechanical strength and bump pitch reduction due to intermetallic compound growth interference, leading to internal stress and limited miniaturization potential.

Innovation Solution

A terminal structure with a convex under-bump metal layer and dome-shaped bump configuration, where the under-bump metal layer thickness at the center is greater than or equal to the thickness at the end portion, and a specific ratio of distances between points on the insulating coating layer ensures reduced growth point interference, enhancing mechanical strength and allowing for closer bump spacing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the conventional bump formation method with concave under-bump metal layer is used, then the manufacturing process is simple, but the mechanical strength at the interface is reduced due to internal stress from IMC phase growth interference

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidinterface mechanical strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The invention inverts the conventional concave shape of the under-bump metal layer into a convex shape. This inversion prevents the intermetallic compound phase from growing in a direction that would cause interference and internal stress, thereby improving interface mechanical strength while maintaining manufacturing simplicity through electroplating processes

Inventive Principle:

Principle #13The other way round (Inversion)

2Strength

If the opening of the passivation layer is extended to mitigate IMC phase growth interference, then the mechanical strength is improved, but the bump pitch cannot be reduced due to increased inter-bump spacing requirement

Engineering Contradiction:

Improveinterface mechanical strengthVSAvoidbump pitch

Core Design Contradiction:

StrengthVSLength of moving object

Solution Approach 1:

The invention applies local quality by creating a convex shape specifically at the under-bump metal layer region rather than extending the opening across the entire passivation layer. This localized convex structure prevents IMC phase growth interference at the critical interface while allowing the opening to remain narrow, thus enabling bump pitch reduction without compromising mechanical strength

Inventive Principle:

Principle #3Local quality

3Strength

If the under-bump metal layer thickness is increased to improve mechanical strength, then the interface robustness is enhanced, but the bump size and pitch are increased

Engineering Contradiction:

Improveinterface mechanical strengthVSAvoidbump size

Core Design Contradiction:

StrengthVSVolume of moving object

Solution Approach 1:

The invention applies spheroidality by forming a convex, dome-like shape of the under-bump metal layer instead of a flat or concave structure. This curved convex shape provides enhanced mechanical strength at the interface by distributing stress more effectively, while the overall bump size remains compact, enabling high-density packaging without sacrificing interface robustness

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 configuration effectively eliminates internal stress, improves mechanical strength, and enables bump pitch reduction while maintaining robustness, suitable for miniaturization of semiconductor devices.

Implementation Method 1

an intermetallic compound (IMC) phase (not shown), which is formed near a boundary between the under-bump metal layer and the bump, grows in a direction substantially perpendicular to the boundary

Methodology Applied

Scientific EffectIntermetallic compound growth:

Implementation Method 2

electroplating is performed, which includes electrolytic nickel plating and electrolytic solder plating in this order, to thereby form a under-bump metal layer 50 and a solder plating layer 60

Methodology Applied

Scientific EffectElectroplating: Electroplating

Implementation Method 3

the entire substrate is placed in a reflow furnace and heated to thereby form a bump 65

Methodology Applied

Scientific EffectReflow heating: Heating

Data Source

PatentUS9640500B2Terminal structure and semiconductor device

Publication Date: 2017.05.02 TDK CORP

AI summary

The present invention relates to a terminal structure comprising; a base material 10; an external electrode 20 formed on the base material; an insulating coating layer 30 formed on the base material and on the electrode and having an opening exposing at least part of the electrode; an under-bump metal layer 70 filling the opening and covering part of the insulating coating layer; and a dome-shaped bump 85 covering the under-bump metal layer, wherein in a cross section along a lamination direction, the under-bump metal layer has a convex shape toward the bump, and the thickness Tu0 of the under-bump metal layer at a center of the opening is equal to or greater than the thickness Tu1 of the under-bump metal layer at an end portion of the opening.