Semiconductor Package Bump Structure for Side-Wetting-Free Cu Bonding

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Solution Overview

Problem

The challenge of side wetting during copper-copper bonding in semiconductor packages, which occurs due to insufficient diffusion at the junction, leading to deteriorated bonding properties, is addressed by using metal bump structures with varying thermal expansion coefficients to enhance bonding quality.

Innovation Solution

The semiconductor package incorporates metal bump structures with copper as the main pattern and a sub-pattern of a metal with a higher thermal expansion coefficient, such as zinc or aluminum, to induce sufficient diffusion during high-temperature annealing, ensuring strong bonding between semiconductor chips.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If copper-copper bonding is used to prevent side wetting, then side wetting is prevented, but bonding properties deteriorate due to insufficient diffusion at the junction

Engineering Contradiction:

Improveside wettingVSAvoidbonding properties

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies local quality by using a multi-layer metal bump structure where the first metal pattern (Cu) provides bulk material and the second metal pattern (Zn or Al) is specifically positioned at the bonding junction surface to enhance diffusion. This local differentiation allows the bonding interface to have superior diffusion properties while the bulk maintains structural integrity, resolving the contradiction between preventing side wetting and ensuring bonding reliability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by combining Cu and Zn (or Al) in a layered metal bump structure. The Cu layer provides mechanical strength and electrical conductivity, while the Zn (or Al) layer at the bonding interface promotes diffusion and prevents side wetting. This composite approach enables simultaneous achievement of both side wetting prevention and enhanced bonding properties.

Inventive Principle:

Principle #40Composite materials

2Reliability

If high temperature and pressure are applied to achieve sufficient diffusion, then bonding properties improve, but device complexity increases

Engineering Contradiction:

Improvebonding propertiesVSAvoidbonding process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the material parameters of the metal bump structure by introducing a second metal pattern with different thermal and diffusion properties (Zn or Al) at the bonding interface. This material parameter change enables effective diffusion and bonding at reduced temperature and pressure compared to traditional Cu-Cu bonding, thereby improving bonding properties while reducing process complexity.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If pitch between chip pads decreases, then device integration increases, but side wetting occurs more frequently

Engineering Contradiction:

Improvedevice integrationVSAvoidside wetting

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by positioning the second metal pattern (Zn or Al) specifically at the bonding junction surface where diffusion is needed, while the first metal pattern (Cu) maintains the bulk structure. This localized approach prevents side wetting at the bonding interface without requiring larger pad pitch, enabling higher device integration while eliminating side wetting issues.

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 provides excellent bonding properties by applying a local load at the junction, enhancing the bonding strength and reliability of the semiconductor package.

Implementation Method 1

the second metal pattern includes a second metal having a second coefficient of thermal expansion greater than the first coefficient of thermal expansion

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

since sufficient diffusion at a junction may occur, a relatively high temperature and pressure may be desired

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS20250329679A1Semiconductor package and method of manufacturing the semiconductor package

Publication Date: 2025.10.23 SAMSUNG ELECTRONICS CO LTD

AI summary

A semiconductor package includes: a first semiconductor device including a first pad and a first metal bump structure on the first pad; and a second semiconductor device on the first semiconductor device, and including a third pad and a second metal bump structure on the third pad, wherein the first and second metal bump structures are bonded to each other to electrically connect the first and second semiconductor devices to each other. Each of the first and second metal bumps structures includes first to third metal patterns. The first to third metal patterns of the first metal bump structure are on the first pad. The first to third metal patterns of the second metal bump structure are on the third pad. The first and third metal patterns include a first metal having a first coefficient of thermal expansion less than that of a second metal of the second metal pattern.