Conductive Barrier Layer for MEMS Through-Glass Via Corrosion
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Solution Overview
Problem
Copper-based through-glass vias in microelectromechanical systems (MEMS) can experience corrosion due to copper migration through gold layers, leading to the formation of contaminants like CuO, which negatively impacts the performance of MEMS components.
Innovation Solution
Applying a conductive barrier layer, such as palladium or nickel, between the copper through-glass via and gold layers using electroless plating techniques like ENIG, EPIG, or IGEPIG to prevent copper migration and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper-based TGV is used to communicate electrical signals, then electrical conductivity is achieved, but copper migration through gold layers causes corrosion and contaminant formation
Solution Approach 1:
A conductive barrier layer comprising nickel and/or palladium is applied between the copper-based TGV and the gold layers. This intermediary layer prevents copper migration into the gold layers while maintaining electrical conductivity, thereby eliminating contaminant formation and corrosion without compromising signal transmission.
2Object-generated harmful factors
If conductive barrier layer is applied to prevent copper migration, then corrosion is reduced, but device structure becomes more complex
Solution Approach 1:
The conductive barrier layer is formed as a composite structure comprising multiple materials (nickel and/or palladium) deposited in sequence. This composite approach provides superior copper migration resistance compared to single-material barriers, while the thin-film nature maintains manufacturing feasibility.
3Reliability
If electroless plating process is used to apply barrier layer, then copper migration is prevented, but manufacturing process complexity increases
Solution Approach 1:
The electroless plating process is a self-service chemical deposition method where the barrier layer forms automatically through chemical reduction reactions without requiring external electrical power. The nickel and/or palladium layers deposit spontaneously from solution onto the copper TGV surface, eliminating the need for complex external plating equipment.
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
The conductive barrier layer effectively reduces or eliminates copper migration and contamination, ensuring reliable performance of MEMS components by maintaining the integrity of gold layers and preventing corrosion at elevated temperatures.
Implementation Method 1
an electrically conductive barrier layer applied between the copper through-glass via (TGV) and any associated gold layers, to reduce or eliminate migration of copper through the gold layers
Implementation Method 2
The method may further comprise applying the conductive barrier layer using an electroless plating process. The electroless plating technique may be electroless palladium and immersion gold (EPIG).
Data Source
AI summary
A method of preventing corrosion associated with an electrically-conductive through-glass via (TGV) may comprise forming a TGV in a glass substrate for use in a microelectromechanical system (MEMS) device. The TGV has a first end and a second end, and at least partially comprises copper. The method may further comprise applying a conductive barrier layer on the first end of the TGV and/or the second end of the TGV, and applying a metal layer over the conductive barrier layer. The method may further comprise extending the conductive barrier layer over the first end of the TGV, and over at least a portion of the glass substrate encompassing the end of the TGV, such that the conductive barrier layer overlaps a boundary between the TGV and the glass substrate.