Solder Bump Confinement via Sputtered Defining Layer
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Solution Overview
Problem
The integration of wire and ball bonds in a single integrated circuit package is challenging due to the incompatibility of aluminum (Al) wire bonds with copper (Cu) pads and tin (Sn) solder bonds, requiring different metal pads and complex masking processes, which are costly and inefficient.
Innovation Solution
A solder bump confinement system is developed, involving a substrate with a contact material, an inner passivation layer, an under bump material defining layer, and a system interconnect, where the under bump material defining layer is formed by sputtering, allowing for compatibility between Al and Cu pads without the need for high temperature processes or additional masking steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different metal pads (Al for wire bonds, Cu for ball bonds) are used in the same integrated circuit package, then compatibility with both wire and ball bonds is achieved, but manufacturing complexity increases due to requiring different masks and additional processing steps
Solution Approach 1:
The bond pad structure is segmented into multiple functional layers: a first metal layer (Al) for wire bond compatibility, a second metal layer (Cu) for ball bond compatibility, and an intermediate layer between them. This segmentation allows each layer to serve its specific function while maintaining overall system compatibility with both bonding methods.
Solution Approach 2:
Different metal compositions are applied to different regions and depths of the bond pad structure. The first metal layer uses Al with specific physical properties for wire bonds, while the second metal layer uses Cu with properties optimized for ball bonds. This local differentiation of material properties enables simultaneous compatibility with both bonding techniques without requiring separate masks for each bond type.
2Adaptability or versatility
If Cu pads are made by thin-film deposition over Al pads, then Cu bond pads for ball bonds can be created, but additional processing steps and masks are required increasing manufacturing cost
Solution Approach 1:
The patent merges the formation of Al and Cu bond pads into a single integrated structure where the first metal layer (Al) and second metal layer (Cu) are deposited and patterned together as a unified multi-layer system. This combined approach eliminates the need for separate masking and deposition processes that would be required if Cu pads were created as distinct features over Al pads, thereby reducing manufacturing cost while maintaining the ability to support both bonding types.
3Area of stationary object
If Al wire bonds are used with Cu bond pads, then bonding compatibility is poor, but using Cu pads reduces package size and increases connection density
Solution Approach 1:
The patent introduces an intermediate layer between the first metal layer (Al) and second metal layer (Cu) that acts as a mediator to ensure proper bonding compatibility. This intermediate layer facilitates reliable Al wire bond attachment to the bond pad structure while maintaining the Cu layer's ability to support ball bonds, thus resolving the incompatibility issue while preserving the space-saving benefits of Cu pads.
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 solution enables a cost-effective and efficient integration of wire and ball bonds in a single package, reducing manufacturing complexity and costs while maintaining performance, by using a sputtered under bump material defining layer that simplifies the manufacturing process and eliminates the need for high temperature processes.
Implementation Method 1
forming an under bump material defining layer over the contact material by sputtering
Data Source
AI summary
A solder bump confinement system is provided includes a substrate; a contact material patterned on the substrate; an inner passivation layer deposited over the contact material and the substrate; an under bump material pad over the contact material; an under bump material defining layer, having a bump opening contained therein, directly on the under bump material pad in which the under bump material defining layer has a thickness in the range of 200 Angstrom to 1500 Angstrom; and a system interconnect formed over the contact material and coupled to the under bump material defining layer and the under bump material pad through the bump opening.