Silicon Bridge Pad Structure Using Silicon Nitride to Reduce Wafer Bowing
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Solution Overview
Problem
Existing silicon bridge technologies face challenges with thick copper pad layers, which lead to increased processing time, wafer bowing issues, and complex fabrication processes.
Innovation Solution
Incorporating a thin silicon nitride layer on top of a copper pad layer, reducing the copper pad thickness to approximately 2 microns, and using a silicon nitride layer for protection and adhesion, thereby simplifying the fabrication process and mitigating wafer bowing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick copper pad layers are used for conductive pads, then adhesion and electrical connection are improved, but processing time increases and wafer bowing occurs
Solution Approach 1:
The conductive pad structure is segmented into multiple functional layers: a thin copper pad layer (2-5 microns) for electrical connection and a thicker silicon nitride layer (10-20 microns) for mechanical support and adhesion. This segmentation allows each layer to be optimized for its specific function, reducing overall processing time while maintaining reliability
Solution Approach 2:
The patent uses a composite structure combining copper and silicon nitride materials. The copper layer provides excellent electrical conductivity and adhesion to the silicon substrate, while the silicon nitride layer provides mechanical strength, adhesion to overlying layers, and stress management. This composite approach achieves both reliability and reduced processing time
2Reliability
If thick copper pad layers are used, then electrical connection is improved, but wafer bowing issues occur
Solution Approach 1:
The pad structure is divided into functional segments where the thin copper layer (2-5 microns) handles electrical functions and the thicker silicon nitride layer (10-20 microns) handles mechanical stability. This segmentation eliminates wafer bowing while preserving electrical connection quality
Solution Approach 2:
The patent changes the thickness parameters of the pad layers: reducing copper thickness to 2-5 microns and increasing silicon nitride thickness to 10-20 microns. This parameter optimization maintains electrical performance while improving wafer flatness and reducing bowing issues
3Reliability
If thick copper pads are used, then adhesion is improved, but fabrication process complexity increases
Solution Approach 1:
The adhesion function is segmented between the copper-silicon interface and the silicon nitride-overlying layers interface. Each interface is optimized independently, simplifying the overall fabrication process while maintaining strong adhesion throughout the structure
Solution Approach 2:
The silicon nitride layer acts as an intermediary between the copper pad and the overlying package layers. It provides a stable adhesion interface that is easier to fabricate and control than thick copper layers, reducing process complexity while maintaining adhesion reliability
Data Source
AI summary
Alternative surfaces for conductive pad layers of silicon bridges for semiconductor packages, and the resulting silicon bridges and semiconductor packages, are described. In an example, a semiconductor structure includes a substrate having a lower insulating layer disposed thereon. The substrate has a perimeter. A metallization structure is disposed on the lower insulating layer. The metallization structure includes conductive routing disposed in a dielectric material stack. First and second pluralities of conductive pads are disposed in a plane above the metallization structure. Conductive routing of the metallization structure electrically connects the first plurality of conductive pads with the second plurality of conductive pads. An upper insulating layer is disposed on the first and second pluralities of conductive pads. The upper insulating layer has a perimeter substantially the same as the perimeter of the substrate.