Solder Bump Connections via Conductive Plug and Passivation
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Solution Overview
Problem
Conventional solder bump connections in semiconductor chip fabrication face challenges in improving adhesion, solder wetting, and diffusion barrier performance, leading to potential reliability issues and increased complexity in the fabrication process.
Innovation Solution
A method involving a layer stack with a conductive plug and dielectric passivation layer, where the plug is formed within a via opening extending through the passivation layer, eliminating the need for chemical mechanical polishing and simplifying the process by integrating the adhesion and seed layers under the plug, and using a barrier layer to promote solder bump formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional BLM layers are used to promote solder bump attachment, then adhesion and solder wetting are improved, but the fabrication process complexity increases due to multiple metallic layers
Solution Approach 1:
The BLM structure is segmented into two distinct conductive layers (first conductive layer and second conductive layer) with different functions. The first conductive layer provides adhesion to the dielectric passivation layer, while the second conductive layer provides solder wetting promotion. This segmentation allows each layer to be optimized for its specific function, improving overall reliability while maintaining process simplicity through the use of only two layers instead of multiple conventional BLM layers.
Solution Approach 2:
The conductive plug serves multiple functions simultaneously: it provides electrical connection through the dielectric passivation layer, acts as an adhesion promoter, and serves as a diffusion barrier. By integrating these multiple functions into a single component (the conductive plug), the invention reduces the number of separate layers needed, thereby simplifying the fabrication process while maintaining or improving solder bump attachment reliability.
2Reliability
If conventional solder bump connections are used, then basic electrical connection is achieved, but thermal undercut and cracking risks increase
Solution Approach 1:
The dielectric passivation layer is formed beforehand to a sufficient thickness that provides a cushioning effect during thermal processing. This pre-formed thick dielectric layer prevents thermal undercut from reaching the conductive layers and prevents cracking by absorbing thermal stress. The via opening is then formed through this pre-cushioned dielectric layer, ensuring that the subsequent solder bump connection is protected against thermal damage throughout the fabrication and assembly process.
3Strength
If dielectric passivation layer is thickened to improve underfilling operations, then mechanical integrity is improved, but via opening fabrication difficulty increases
Solution Approach 1:
The via opening is formed through the thick dielectric passivation layer before the conductive layers are deposited. This preliminary action ensures that the via opening is precisely formed and positioned while the dielectric layer is still in its optimal state for etching. By performing this difficult fabrication step before adding the conductive layers, the overall manufacturing process becomes easier, as the via opening formation is not complicated by the presence of additional sensitive layers.
Data Source
AI summary
Solder bump connections and methods for fabricating solder bump connections. The method includes forming a layer stack containing first and second conductive layers, forming a dielectric passivation layer on a top surface of the second conductive layer, and forming a via opening extending through the dielectric passivation layer to the top surface of the second conductive layer. The method further includes forming a conductive plug in the via opening. The solder bump connection includes first and second conductive layers comprised of different conductors, a dielectric passivation layer on a top surface of the second conductive layer, a via opening extending through the dielectric passivation layer to the top surface of the second conductive layer, and a conductive plug in the via opening.