Multi-Layer Bonding Pad Structure for IC Substrates
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Solution Overview
Problem
As semiconductor device packing density increases, the high inductance created by bonding pads and wires obstructs high-speed operation due to the need for longer conductive traces and the reliability of the bonding process is critical, especially since problems in wire bonding impact already tested and sorted dies.
Innovation Solution
A novel multi-layer bonding pad or bump structure is directly bonded to a copper or aluminum pad on an IC substrate, using an embossing process, with an electrically conductive adhesion/barrier layer and a bonding metal layer, compatible with wire bonding, TAB, COF, and COG processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bonding pads are disposed on the peripheral of the chips to prevent wire shifting, then wire bonding reliability is improved, but longer conductive traces are needed which increases inductance and obstructs high-speed operation
Solution Approach 1:
The bonding pad structure transitions from a planar configuration to a three-dimensional multi-layer structure. The bonding pad extends through multiple metal interconnect layers (first metal layer, second metal layer, third metal layer) vertically, allowing the bonding interface to be positioned optimally for wire bonding while maintaining short horizontal trace lengths, thereby reducing inductance without compromising bonding reliability
Solution Approach 2:
The bonding pad is constructed as a composite structure comprising multiple metal layers (copper, aluminum, or copper alloy) stacked vertically and connected through conductive vias. This composite arrangement allows the bonding pad to simultaneously provide mechanical support for reliable wire bonding and electrical connection with minimized inductance through optimized current path geometry
2Adaptability or versatility
If the number of I/O connections is increased to meet higher chip capabilities, then chip functionality is improved, but the inductance in connections increases which obstructs high-speed operation
Solution Approach 1:
By utilizing the vertical dimension through multiple metal interconnect layers, the invention accommodates increased I/O connections without proportionally increasing trace lengths. Each bonding pad can be independently positioned and connected through optimized vertical pathways, allowing high-density I/O configurations while maintaining low inductance characteristics essential for high-speed operation
3Area of stationary object
If device packing density is increased to reduce chip size, then chip area is reduced, but more metal interconnect layers are needed which increases complexity
Solution Approach 1:
The multi-layer metal interconnect structure serves multiple functions simultaneously: it provides routing for signal transmission, establishes vertical electrical connections between different chip levels, and forms the bonding pad structure itself. This multi-functionality reduces the need for separate dedicated structures, thereby managing complexity while enabling high device packing density
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 enhances the reliability and compatibility of bonding processes, reducing inductance and improving high-speed operation by creating a secure and efficient electrical connection, suitable for advanced semiconductor devices.
Implementation Method 1
A connecting wire is bonded to connect each bonding pad to a respective contact on the package substrate, using a method such as ultrasonic bonding
Data Source
AI summary
A bonding pad structure is fabricated on an integrated circuit (IC) substrate having at least a contact layer on its top surface. A passivation layer covers the top surface of the IC substrate and the contact layer. The passivation layer has an opening exposing a portion of the contact layer. An electrically conductive adhesion/barrier layer directly is bonded to the contact layer. The electrically conductive adhesion/barrier layer extends to a top surface of the passivation layer. A bonding metal layer is stacked on the electrically conductive adhesion/barrier layer.