Ti/TaN/Au Air-Bridge Wiring for Electromigration Resistance
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Solution Overview
Problem
The miniaturization of semiconductor devices leads to increased parasitic capacitance between wirings, making high-frequency operations challenging, and the use of air-bridge wiring structures with gold (Au) is prone to electromigration issues due to Au's softness and high conductivity, which can cause disconnection under high current conditions.
Innovation Solution
The implementation of a Ti/TaN/Au laminated air-bridge wiring structure, where a tantalum nitride (TaN) layer with a nitrogen concentration of at least 48% is used to enhance electromigration resistance, supported by a Ta/TaN laminated film, which reduces substrate temperature and maintains structural integrity under high current flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If air-bridge wiring with gold (Au) is used to reduce parasitic capacitance, then high-frequency operation is enabled, but electromigration resistance deteriorates due to Au's softness and high conductivity under high current conditions
Solution Approach 1:
The patent employs a Ti/Pt/Au laminated structure where titanium provides adhesion to the substrate, platinum supports the gold layer and provides structural strength, and gold maintains low resistance and high-frequency performance. This composite material approach combines the advantages of each material while mitigating their individual weaknesses, particularly protecting the soft gold from electromigration through the supporting platinum layer.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the metal layers by controlling thickness ratios and material composition. Specifically, the platinum layer thickness is optimized to provide sufficient support to the gold layer, while the gold layer thickness is controlled to maintain low resistance. This parameter optimization ensures both high-frequency operation and electromigration resistance.
2Volume of moving object
If wiring distance is narrowed to achieve miniaturization, then manufacturing cost is reduced, but parasitic capacitance between wirings increases making high-frequency operation difficult
Solution Approach 1:
The patent transitions from planar wiring to three-dimensional air-bridge wiring, where conductors cross over each other in the vertical dimension rather than lying flat in the same plane. This dimensional change allows wiring intersections without increasing parasitic capacitance, enabling miniaturization while maintaining high-frequency performance.
Solution Approach 2:
The patent introduces an insulation film as an intermediary between crossing wirings in the air-bridge structure. This intermediate layer electrically isolates the conductors while allowing them to cross close together, reducing parasitic capacitance compared to conventional planar wiring where conductors would need larger spacing.
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 Ti/TaN/Au laminated film structure effectively reduces parasitic capacitance and increases electromigration resistance, enabling stable high-frequency operations and preventing air-bridge wiring disconnection, even under high current conditions.
Implementation Method 1
the Ta/TaN laminated film, which reduces substrate temperature and maintains structural integrity under high current flows
Data Source
AI summary
A semiconductor device includes a first wiring extending in a first direction and a second wiring extending in a second direction which crosses the first direction and being disposed with a space interposed between the first wiring and the second wiring, and including a tantalum layer, a tantalum nitride layer formed over the tantalum layer, and a metal layer formed over the tantalum nitride layer.