UBM Capping Structure for Planar Void-Resistant Solder Joints
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Solution Overview
Problem
Existing semiconductor packaging technologies face challenges in achieving high planarity at the outermost surfaces of semiconductor structures, leading to potential void formation during solder joint processes, which affects the reliability and performance of the semiconductor devices.
Innovation Solution
A semiconductor structure is fabricated with a cap structure over an under-bump metallization (UBM) and a capping layer that provides high degrees of planarity, suppressing or eliminating voids in the solder joint process, and includes a redistribution circuit structure for electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional semiconductor packaging processes are used, then manufacturing simplicity is maintained, but planarity at the outermost surfaces deteriorates leading to void formation
Solution Approach 1:
The patent applies preliminary action by forming the capping layer over the UBM structure before the solder joint process. This capping layer is specifically designed to provide high planarity at the outermost surface, preventing void formation during subsequent soldering operations. The cap structure is prepared in advance with the appropriate topography to ensure planarity is maintained throughout the manufacturing process.
Solution Approach 2:
The capping layer acts as an intermediary element between the UBM structure and the solder joint. This intermediate layer mediates the interface by providing a planar surface that eliminates void formation, while also serving as a bridge for electrical and mechanical connectivity between the underlying metallization and the solder bump.
2Reliability
If cap structure with capping layer is added, then planarity and void suppression are improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple functions into the cap structure and capping layer combination. The cap structure provides mechanical support and structural definition, while the capping layer simultaneously provides planarity, void suppression, and electrical connectivity. This merging of functions reduces the need for separate components and processes, thereby simplifying overall manufacturing despite the added structural elements.
Solution Approach 2:
The capping layer serves multiple functions: it provides high planarity at the outermost surface, suppresses void formation during soldering, maintains electrical connectivity through the UBM structure, and supports the solder joint mechanically. This multi-functionality reduces the need for additional specialized components, offsetting the complexity increase with functional consolidation.
3Productivity
If planarity is not maintained, then manufacturing simplicity is preserved, but void formation increases affecting device performance
Solution Approach 1:
The capping layer is formed in advance before the solder joint process to establish the required planarity. This preliminary action ensures that when the soldering process occurs, the surface is already optimized for void-free bonding, eliminating the need for complex real-time adjustments or post-processing steps that would reduce manufacturing efficiency.
Data Source
AI summary
A semiconductor structure includes a semiconductor die, a redistribution circuit structure, and a terminal. The redistribution circuit structure is disposed on and electrically coupled to the semiconductor die. The terminal is disposed on and electrically coupled to the redistribution circuit structure, where the redistribution circuit structure is disposed between the semiconductor die and the terminal, and the terminal includes an under-bump metallization (UBM) and a capping layer. The UBM is disposed on and electrically coupled to the redistribution circuit structure, where the UBM includes a recess. The capping layer is disposed on and electrically coupled to the UBM, where the UBM is between the capping layer and the redistribution circuit structure, and the capping layer fills the recess of the UBM.