Selective Metal Bonding Layer for Aluminum-Copper Passive Interfaces

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Solution Overview

Problem

The bonding between aluminum and copper in integrated passive devices is poor due to the formation of brittle intermetallic compounds, leading to difficulties in creating suitable joints and resulting in lower performing devices with limited longevity and reliability, especially in harsh environments.

Innovation Solution

The use of a vapor phase metal bonding material is applied to create a bonding layer between the aluminum and copper components, enhancing the metallurgical bonding and stability of the interface through the deposition of a bonding material layer on selected areas, which improves the electrical connection and mechanical stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If aluminum and copper are directly bonded to create integrated passive devices, then device performance and conductivity are improved, but the bonding reliability deteriorates due to formation of brittle intermetallic compounds

Engineering Contradiction:

Improvebonding reliabilityVSAvoidbrittle intermetallic compounds

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

A bonding material layer is introduced as an intermediary between the aluminum capacitor components and copper interconnects. This bonding material serves as a mediator that prevents direct contact between aluminum and copper, thereby avoiding the formation of brittle intermetallic compounds while maintaining electrical connectivity and mechanical bonding reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention employs a composite structure consisting of multiple materials: aluminum capacitor components, bonding material layer, and copper interconnects. This composite approach allows each material to perform its optimal function - aluminum for capacitance, bonding material for reliable interface, and copper for low-resistance interconnection - while avoiding the harmful aluminum-copper intermetallic reaction.

Inventive Principle:

Principle #40Composite materials

2Duration of action of stationary object

If conventional aluminum-copper bonding is used, then manufacturing simplicity is maintained, but device longevity and stability deteriorate in harsh environments

Engineering Contradiction:

Improvedevice longevityVSAvoidbonding process complexity

Core Design Contradiction:

Duration of action of stationary objectVSDevice complexity

Solution Approach 1:

The bonding material layer is applied to the aluminum capacitor components before the copper interconnects are formed. This preliminary action ensures that the protective and bonding interface is established in advance, preventing direct aluminum-copper contact and ensuring long-term reliability in harsh environments before any potential degradation can occur.

Inventive Principle:

Principle #10Preliminary action

3Strength

If aluminum capacitor components are directly connected to copper interconnects, then electrical connection is achieved, but mechanical stability deteriorates due to poor bonding

Engineering Contradiction:

Improvemechanical stabilityVSAvoidpoor bonding

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The bonding material layer acts as a mediator that provides both mechanical and electrical interface between aluminum and copper. It adheres to both materials, creating a stable mechanical bond while maintaining electrical conductivity, thereby eliminating the poor bonding issue inherent in direct aluminum-copper contact.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 reduces aerial resistance, enhances stability, and meets industry standards for reliability in harsh environments by creating a stable and reliable interface between dissimilar metal layers, thereby improving the performance and longevity of integrated passive devices.

Implementation Method 1

bonding between components of the device with different metals such as copper and aluminum may improved by depositing a vapor phase metal bonding material

Methodology Applied

Scientific EffectVapor phase deposition: Physical Vapour Deposition

Data Source

PatentUS12191346B1Selective area metal process for improved metallurgical bonding of aluminum to copper for integrated passive devices in a semiconductor device

Publication Date: 2025.01.07 SARAS MICRO DEVICES INC

AI summary

An integrated passive device has a device core of a first metal material and defined by a first side and a second side. Conducting polymer layers are disposed on each of the first side and the second side, and a pattern of one or more direct recesses to the device core are defined in the conducting polymer layers. Bonding material layers are on at least selected areas of the device core that are generally coextensive with the pattern of one or more direct recesses in the conducting polymer layers. First conductive structures of a second metal material different from the first metal material extend from the first side and the second side of the device core. Each of the conductive structures are bonded to a respective one of the bonding material layers. An insulating dielectric encapsulates at least the device core and the conducting polymer layers.