Seed Layer Structure for High Aspect Ratio Vias
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Solution Overview
Problem
Conventional seed layers in high aspect ratio vias fail to provide adequate adhesion for copper filling materials, leading to reliability issues such as open via failures due to poor adhesion between the barrier layer and copper, resulting in high failure rates during thermal stress tests.
Innovation Solution
A seed layer structure with a thicker bottom corner portion compared to the upper portion, formed using physical vapor deposition (PVD) techniques, ensures improved adhesion between the barrier layer and the subsequently formed copper, reducing the risk of copper pullback and enhancing connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional uniform seed layer is formed in high aspect ratio vias, then the manufacturing process is simple, but the adhesion between barrier layer and copper is insufficient leading to open via failures
Solution Approach 1:
The patent applies local quality by creating a non-uniform seed layer thickness distribution where the bottom corner portion has greater thickness than the upper portion. This localized thickness variation provides enhanced adhesion at the critical bottom corner region where stress concentration occurs during thermal cycling, while maintaining thinner thickness in upper regions to preserve manufacturing efficiency.
Solution Approach 2:
The patent implements asymmetry by deliberately designing the seed layer with asymmetric thickness distribution - thicker at the bottom corner and thinner at the upper portion. This asymmetric structure addresses the non-uniform stress distribution in high aspect ratio vias during thermal stress tests, preventing copper pullback at the vulnerable bottom corner interface between barrier layer and copper.
2Reliability
If the seed layer thickness is increased uniformly throughout the via, then adhesion may improve, but material consumption and process time increase
Solution Approach 1:
The patent applies local quality by creating a non-uniform seed layer thickness distribution where the bottom corner portion has greater thickness than the upper portion. This localized thickness variation provides enhanced adhesion at the critical bottom corner region where stress concentration occurs during thermal cycling, while maintaining thinner thickness in upper regions to preserve manufacturing efficiency.
Solution Approach 2:
The patent applies partial action by concentrating the additional seed layer material only where it is most needed - the bottom corner portion - rather than uniformly increasing thickness throughout the entire via. This targeted approach provides sufficient adhesion improvement at the critical interface while minimizing overall material consumption.
3Manufacturing precision
If photolithography and etching processes are used to form dual damascene openings, then precise patterning is achieved, but the process complexity and manufacturing time increase
Solution Approach 1:
The patent applies preliminary action by pre-forming the non-uniform seed layer structure with enhanced bottom corner thickness before copper filling. This preliminary structuring of the seed layer ensures adequate adhesion is established in advance, preventing copper pullback during subsequent electroplating and thermal stress tests, thereby ensuring manufacturing precision is maintained without requiring additional corrective steps.
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 proposed seed layer structure significantly reduces open via failure rates from 70% to 0% during humidity thermal stress tests, ensuring reliable connections by improving adhesion and preventing copper pullback.
Implementation Method 1
The seed layer may be formed by using suitable fabrication techniques such as PVD, electroless plating and the like
Data Source
AI summary
A seed layer comprises a bottom seed layer portion formed on the bottom of a via opening, a sidewall seed layer portion formed on an upper portion of the sidewall of the via opening and a corner seed layer portion formed between the bottom seed layer portion and the sidewall seed layer portion. The sidewall seed layer portion is of a first thickness. The corner seed layer portion is of a second thickness and the second thickness is greater than the first thickness.