Semiconductor Bump Structure Fabrication via Encapsulating Layer
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Solution Overview
Problem
The existing bumping process in semiconductor devices faces issues with undercutting during wet etching of the under-bump metallization (UBM) layer, leading to stress concentration, sidewall delamination, and premature failure of solder bumps, especially in fine pitch designs.
Innovation Solution
A method is introduced that forms an encapsulating layer with a second opening, where the UBM layer is selectively deposited and a bump layer is formed within this opening, eliminating the need for UBM etching and reducing undercut issues, while the encapsulating layer replaces the conventional photoresist mask, allowing for a more robust bump structure with enhanced reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wet etching is used to remove the UBM layer, then the UBM layer can be effectively removed, but undercutting occurs leading to stress concentration and bump sidewall delamination
Solution Approach 1:
The patent replaces the chemical wet etching process with a mechanical removal process. Specifically, the UBM layer is removed by peeling or delaminating it from the substrate using a release layer, rather than using chemical etchants. This mechanical approach eliminates the isotropic etching that causes undercutting, while still achieving complete UBM layer removal.
Solution Approach 2:
The patent introduces a release layer as an intermediary between the UBM layer and the substrate. This release layer facilitates the mechanical removal of the UBM layer by providing a plane of separation, allowing the UBM to be peeled away without damaging the underlying substrate or causing undercutting at the edges.
2Reliability
If conventional photoresist mask is used, then the bumping process can be completed, but the encapsulating layer cannot prevent electrical shorts or environmental stresses
Solution Approach 1:
The encapsulating layer serves multiple functions simultaneously: it acts as a structural support for the bump, provides electrical insulation to prevent shorts between adjacent bumps, protects against environmental stresses, and serves as the masking layer during the bumping process. This multi-functionality eliminates the need for separate photoresist masks and dedicated protective layers.
Solution Approach 2:
The patent merges the functions of the encapsulating layer with the masking and protection functions traditionally performed by separate photoresist layers and protective coatings. The encapsulating layer is formed as part of the substrate structure and performs both structural and electrical isolation functions, simplifying the overall device architecture.
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
This approach results in a robust bump structure with improved strength and reliability, reducing the risk of bump bridging and enabling finer pitch designs with increased reliability and reduced defects, as the encapsulating layer prevents electrical shorts and protects the substrate from environmental stresses.
Implementation Method 1
forming an encapsulating layer with a second opening
Implementation Method 2
the UBM layer is selectively deposited and a bump layer is formed within this opening
Data Source
AI summary
A method for fabricating bump structure forms an under-bump metallurgy (UBM) layer in an opening of an encapsulating layer, and then forms a bump layer on the UBM layer within the opening of the encapsulating layer. After removing excess material of the bump layer from the upper surface of the encapsulating layer, the encapsulating layer is removed till a top portion of the bump layer protrudes from the upper surface of the encapsulating layer.