Underbump Metallization Dry Etch for Uniformity
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Solution Overview
Problem
Current methods for forming contact layers with solder bumps in integrated circuits face challenges such as complex wet chemical etch processes, which lead to non-uniformities, material loss, and increased production costs, due to pattern-dependent etch rates and interactions with bump material, affecting mechanical and electrical integrity.
Innovation Solution
A dry etch process is used to pattern the underbump metallization layer, reducing dependence on pattern density and allowing for more flexible design, with a plasma-based etch process for the second layer, and an electrochemical etch process for the first layer, to improve uniformity and reduce material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet chemical etch process is used to pattern the underbump metallization layer, then the etching can be performed with standard chemistry, but the etch rate becomes pattern-dependent leading to non-uniformities and material loss
Solution Approach 1:
The patent changes the etching method from wet chemical etching to plasma-based dry etching. This parameter change eliminates the pattern-dependent etch rate issue because plasma etching provides more uniform etching across different bump configurations, thereby improving solder bump uniformity while maintaining manufacturability through a controlled dry etch process
Solution Approach 2:
The patent replaces the wet chemical etching system with a plasma-based dry etching system. This substitution eliminates the harmful interactions between wet chemistry and bump material, reducing material loss and improving manufacturing precision without significantly increasing process complexity
2Ease of manufacture
If wet chemical etch process is used to pattern the underbump metallization layer, then the etching can be performed with standard chemistry, but material loss occurs affecting mechanical and electrical integrity
Solution Approach 1:
The patent replaces wet chemical etching with plasma-based dry etching, which eliminates the chemical interactions that cause bump material loss. The dry etch process physically removes material without the harmful chemical reactions present in wet etching, thereby preserving bump material integrity while maintaining ease of manufacture through a standardized plasma process
Solution Approach 2:
The patent uses a plasma-based dry etch process that operates in a controlled inert atmosphere. This inert environment prevents harmful chemical interactions between the etching chemistry and the bump material, eliminating material loss and preserving the mechanical and electrical integrity of the solder bumps
3Ease of manufacture
If electroplating is used to deposit solder bump material, then deposition can be performed without complex mask technology, but a continuous and uniform current distribution layer is required which constrains the underbump metallization design
Solution Approach 1:
The patent divides the underbump metallization into multiple functional layers with different properties. This segmentation allows the current distribution layer to be optimized for electroplating uniformity while other layers maintain design flexibility for adhesion and diffusion barrier functions, thereby resolving the constraint on overall design versatility
Solution Approach 2:
The patent applies different material properties to different regions or functions within the underbump metallization structure. The current distribution layer is specifically designed with uniform properties for electroplating, while other layers can have varying compositions to maintain adhesion and barrier functions, thus preserving overall design adaptability
4Reliability
If the underbump metallization layer is patterned to provide diffusion barrier, then solder material migration is prevented, but the layer thickness and resistance must be carefully controlled to avoid increasing overall system resistance
Solution Approach 1:
The patent divides the diffusion barrier function across multiple layers in the underbump metallization stack. This segmentation allows each layer to be optimized for its specific function - some layers provide diffusion barrier while others provide current conduction - thereby achieving reliable protection without requiring any single layer to be excessively thick, thus maintaining low overall resistance
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 enhances device performance and reduces production costs by improving solder bump uniformity and mechanical integrity, while allowing for more flexible design and increased yield, independent of bump configuration and size.
Implementation Method 1
a plasma-based etch process for the second layer
Implementation Method 2
an electrochemical etch process for the first layer
Data Source
AI summary
By patterning the underbump metallization layer stack on the basis of a dry etch process, significant advantages may be achieved compared to conventional techniques involving a highly complex wet chemical etch process. In particular embodiments, a titanium tungsten layer or any other appropriate last layer of an underbump metallization layer stack may be etched on the basis of a plasma etch process using a fluorine-based chemistry and oxygen as a physical component. Moreover, appropriate cleaning processes may be performed for removing particles and residues prior to and after the plasma-based patterning process.