Copper Wire Bonding via Gold Bump to Prevent Insulating Film Breakage
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Solution Overview
Problem
Copper wires, with lower electrical resistance than gold, are harder and more difficult to form into thin wires, leading to stress issues during wire bonding that can break the interlayer insulating film and cause short-circuits in semiconductor devices with closely arranged electrode pads, reducing device reliability.
Innovation Solution
A copper wire bonding technique using a bump made of a softer metal, such as gold, is formed between the copper wire and the electrode pad to absorb stress and prevent film breakage, with a wide width part of the copper wire joined to the pad via this bump to reduce impedance and improve manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper wire is used to reduce electrical resistance, then electrical resistance is reduced, but the wire becomes harder and may break the interlayer insulating film during bonding
Solution Approach 1:
A bump made of softer metal material (such as gold) is formed between the copper wire and the electrode pad to serve as an intermediary. This bump absorbs the stress generated during wire bonding, preventing the hard copper wire from breaking the interlayer insulating film while maintaining the low electrical resistance of the copper wire connection path.
2Reliability
If copper wire diameter is increased to reduce impedance, then impedance is reduced, but neighboring wires may short-circuit due to narrow arrangement pitch
Solution Approach 1:
The copper wire is divided into two functional parts: a wire diameter part for electrical conduction and a wide width part for mechanical bonding. This segmentation allows the wire diameter part to be thin (reducing short-circuit risk) while the wide width part provides sufficient bonding area, thus maintaining low impedance without increasing short-circuit risk.
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 the reliability of semiconductor devices by preventing interlayer film breakage and short-circuits, while maintaining low impedance and efficient manufacturing processes.
Implementation Method 1
a bump made of a metal material having a hardness lower than that of copper... the stress at the time of crimping is transmitted to an interlayer insulating film... and there arises such a problem that the interlayer insulating film etc. is broken
Implementation Method 2
Copper has a still lower electrical resistance compared to that of gold... from the viewpoint of reduction in impedance, it is preferable for the wire diameter to have a certain magnitude
Data Source
AI summary
To improve reliability of a semiconductor device in which wire bonding using a wire made of copper is performed. A semiconductor device is configured so that one of end parts (wide width part) of a copper wire is joined via a bump on a pad (electrode pad) formed over a main surface (first main surface) of a semiconductor chip of the semiconductor device. The bump is made of gold, which is a metal material having a hardness lower than that of copper, and the width of the bump is narrower than the width of the wide width part of the wire.