Non-oxidizing Metal Interconnects for Copper IC Die
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Solution Overview
Problem
Copper interconnects in image sensors are prone to oxidation when exposed to air, compromising their conductivity, while alternative metals like aluminum offer lower conductivity.
Innovation Solution
Using corrosion-resistant metals like tungsten in VIAs and pre-contacts external to the seal ring, preventing copper from extending beyond the internal seal ring and thus avoiding oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If copper is used for interconnects, then electrical conductivity is improved, but oxidation resistance deteriorates when exposed to air
Solution Approach 1:
The interconnect structure is divided into two segments: an internal portion made of copper for high conductivity within the seal ring, and an external portion made of corrosion-resistant metal (such as tungsten, titanium, or tantalum) extending outside the seal ring. This segmentation allows each material to perform its optimal function while preventing copper oxidation exposure to air.
Solution Approach 2:
A corrosion-resistant metal layer acts as an intermediary between the copper interconnect and the external environment. This intermediary layer prevents direct contact between copper and air, eliminating oxidation while maintaining electrical conductivity through the corrosion-resistant material that bridges the copper to external circuitry.
2Reliability
If aluminum is used instead of copper, then oxidation resistance is improved, but electrical conductivity deteriorates
Solution Approach 1:
The interconnect is segmented into two functional zones: the internal copper portion provides superior electrical conductivity for signal and power transmission within the sealed environment, while the external corrosion-resistant metal portion provides oxidation resistance for exposure to air, eliminating the need to use aluminum throughout the entire interconnect structure.
Solution Approach 2:
Different materials with specific properties are applied to different locations: copper with high conductivity is used where electrical performance is critical (internal to seal ring), while corrosion-resistant metals with oxidation resistance are used where environmental exposure is the concern (external to seal ring), optimizing both conductivity and reliability in their respective locations.
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
Enables the use of copper for its high conductivity within the seal ring without exposing it to air, maintaining performance while preventing corrosion.
Implementation Method 1
the buses are made of either aluminum (Al) or copper (Cu)... Using copper internal of the seal ring... maintaining performance while preventing corrosion
Implementation Method 2
extending the copper outside the internal seal ring exposes the copper to air and the like which causes the copper to be oxidized... corrosion resistant metals in the VIAs and pre-contacts... preventing copper from extending beyond the internal seal ring and thus avoiding oxidation
Data Source
AI summary
An integrated circuit includes a substrate; a sealing element spanning a periphery of the substrate that forms a protective boundary for the substrate; a plurality of copper lines spanning the substrate in at least two distinct layers contained within the protective boundary; a first conducting element disposed outside the sealing element; and one or more second conducting elements connecting at least two of the copper lines and that spans the sealing element; wherein the conducting elements are substantially non-oxidizing metals that are resistant to oxidization and that connect the copper line to the first conducting element.