Metal Pad Polymer Plugs for IC Transition Stress
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Solution Overview
Problem
In the formation of integrated circuits, the transition regions between metal pads and interconnect traces are prone to cracking due to rigidity, which can lead to structural stress and failure during manufacturing and usage.
Innovation Solution
The introduction of polymer plugs extending into the metal pads through openings in the polymer layers, which reduces the rigidity of the transition regions and helps absorb stress, is achieved by forming a Post-Passivation Interconnect (PPI) structure with specific dimensions and configurations, including PPI pads and traces, and Under-Bump-Metallurgy (UBM) connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the transition regions between metal pads and interconnect traces are made rigid to maintain structural stability, then structural stability is improved, but cracking occurs due to stress during manufacturing and usage
Solution Approach 1:
The patent applies local quality by creating a polymer plug specifically in the transition region between the metal pad and interconnect trace, while leaving other regions unchanged. This localized modification reduces rigidity only where needed (in the high-stress transition zone) while maintaining structural stability in other areas, thereby preventing cracking without compromising overall structural integrity.
Solution Approach 2:
The patent changes the physical parameter of rigidity in the transition region by introducing a polymer plug with different mechanical properties than the surrounding materials. This parameter change (from rigid to more flexible) allows the transition region to absorb stress and prevent cracking, while the rest of the structure maintains its original rigidity and stability.
2Reliability
If polymer plugs are introduced into metal pads to reduce rigidity and absorb stress, then cracking resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the polymer plug in the transition region before subsequent manufacturing steps such as UBM deposition and solder ball placement. This advance preparation ensures that the stress-absorbing structure is already in place to prevent cracking during later high-stress operations, while allowing the rest of the manufacturing process to proceed with standard techniques.
Data Source
AI summary
A device includes a metal pad, and a passivation layer comprising portions overlapping edge portions of the metal pad. The metal pad and the passivation layer are in a chip. A solder region is over the passivation layer. A metallic feature electrically inter-couples the metal pad and the solder region, and the metallic feature includes a continuous metal region. A polymer layer includes an upper portion over the metallic feature, and a lower portion penetrating through the continuous metal region.