Passivation Layer Surface Modification for Terminal Metal-Free Bump Metallization
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Solution Overview
Problem
The existing process flow for forming solder bumps in integrated circuits is complex and costly, requiring a terminal metal layer stack that increases production costs and defect rates, and omits the use of well-established process regimes for forming efficient underbump metallization layers without significant process adaptations.
Innovation Solution
A method to form a passivation layer with adjusted surface characteristics to mimic the conditions of a terminal metal layer stack, allowing for the deposition of an underbump metallization layer without the terminal metal layer, thereby reducing process complexity and costs while maintaining similar process results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a terminal metal layer stack is used in the existing process flow, then the bump metallization process achieves reliable solder bump formation, but the production costs and defect rates increase due to the complexity of the process
Solution Approach 1:
The patent extracts and removes the terminal metal layer stack (aluminum-based terminal metal layers) from the existing process flow. By eliminating these intermediate layers, the process complexity is reduced while maintaining the essential functionality of solder bump formation through direct deposition on the passivation layer.
Solution Approach 2:
The patent merges the functions of the terminal metal layer and the underbump metallization layer into a single integrated structure. The underbump metallization layer directly contacts both the passivation layer and the solder bump, combining the roles of terminal metal and bump metallization that were previously separate layers.
2Manufacturing precision
If a terminal metal layer stack is deposited and patterned, then adequate contact areas are provided for solder bumps, but the production costs increase
Solution Approach 1:
The patent extracts the terminal metal layer deposition and patterning steps from the manufacturing process. By removing these costly processing steps, the production cost is reduced while the underbump metallization layer directly provides the necessary contact areas on the passivation layer.
Solution Approach 2:
The underbump metallization layer is designed to perform multiple functions simultaneously: it serves as the contact area foundation, provides metallization for solder bump formation, and eliminates the need for separate terminal metal layers. This multi-functionality reduces the number of processing steps required.
3Device complexity
If the passivation layer surface characteristics are adjusted to mimic terminal metal layer conditions, then underbump metallization can be deposited without terminal metal layers, but additional surface adjustment processes are required
Solution Approach 1:
The patent applies preliminary surface treatment to the passivation layer before depositing the underbump metallization layer. By pre-adjusting the surface characteristics (such as roughness, cleanliness, or chemical composition) to mimic the conditions that would exist with a terminal metal layer, the subsequent metallization deposition proceeds effectively without requiring the terminal metal layer itself.
Data Source
AI summary
By determining at least one surface characteristic of a passivation layer stack used for forming a bump structure, the situation after the deposition and patterning of a terminal metal layer stack may be “simulated,” thereby providing the potential for using well-established bump manufacturing techniques while nevertheless significantly reducing process complexity by omitting the deposition and patterning of the terminal metal layer stack.