Selective Metal Bonding for Copper-Aluminum Passive Device Vias
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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 lower performing devices and difficulty in producing suitable joints without complex chemical processes or organic-based additives.
Innovation Solution
A vapor phase metal bonding material is used to improve metallurgical bonding between copper and aluminum by depositing a bonding material layer on selected areas of the device core, which is then encapsulated with an insulating dielectric and filled with a second metal material to form conductive vias and terminal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used as interconnect material to reduce resistance, then electrical performance is improved, but bonding reliability deteriorates due to brittle intermetallic compounds forming between copper and aluminum
Solution Approach 1:
A titanium bonding layer is introduced as an intermediary between the copper interconnect and aluminum capacitor electrodes. This titanium layer prevents the formation of brittle intermetallic compounds by serving as a diffusion barrier and bonding mediator, enabling reliable metallurgical bonding between dissimilar metals without direct copper-aluminum contact.
Solution Approach 2:
The patent creates a composite metallurgical structure consisting of multiple layers: copper interconnect, titanium bonding layer, and aluminum capacitor electrode. This composite structure combines the low resistance of copper with the bonding reliability of titanium-aluminum metallurgy, achieving both electrical performance and mechanical strength.
2Reliability
If complex chemical processes or organic-based additives are used to improve adhesion between aluminum and copper, then bonding quality is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the need for complex chemical processes and organic-based additives by replacing them with a simple titanium deposition step. The titanium layer provides inherent bonding capability through physical vapor deposition or sputtering, removing the complexity of chemical adhesion promoters while maintaining strong metallurgical bonds.
Solution Approach 2:
The patent replaces chemical bonding mechanisms (requiring complex chemical processes and organic additives) with physical metallurgical bonding through titanium deposition. This substitution uses physical vapor deposition or sputtering processes to create strong metallic bonds without requiring complex chemical treatments.
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 method enhances the stability and reliability of the metallurgical structure, reducing aerial resistance and meeting industry standards for devices in harsh environments.
Implementation Method 1
A vapor phase metal bonding material is used to improve metallurgical bonding between copper and aluminum by depositing a bonding material layer on selected areas of the device core
Data Source
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.