Coated Bonding Wire Sacrificial Layer Oxidation
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Solution Overview
Problem
During the wire bonding process in semiconductor devices, mechanical stresses can cause cracks or openings in the coating layers of wires, leading to localized exposure of the underlying wire material to oxidation, which reduces the electrical performance and increases susceptibility to corrosion.
Innovation Solution
A coated wire structure is employed, featuring a central core material coated with a sacrificial layer that is more chemically active than the core and a protective layer that is less chemically active, where the sacrificial layer oxidizes preferentially to reduce exposure of the core material to oxidation, even when stress-induced openings occur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wire is coated with a protective layer to resist oxidation, then the wire's resistance to oxidation is improved, but stress during bonding may create openings in the coating, exposing the underlying wire material to oxidation
Solution Approach 1:
A sacrificial coating layer is introduced as an intermediary between the core wire material and the environment. This sacrificial layer preferentially oxidizes when stress-induced openings occur, protecting the underlying core material from oxidation. The sacrificial coating acts as a mediator that sacrifices itself to prevent harm to the core material.
Solution Approach 2:
The patent converts the harmful effect of oxidation into a beneficial protective mechanism. By applying a sacrificial coating that is more susceptible to oxidation than the core material, the oxidation process is redirected away from the core material and toward the sacrificial coating, thereby protecting the core material while still allowing oxidation to occur in a controlled manner.
2Reliability
If a sacrificial coating is applied to protect the core material, then the core material is protected from oxidation, but the bonding process may still create stress-induced openings in the coating
Solution Approach 1:
The patent accepts that stress-induced openings will occur but converts this potential failure mode into a protective mechanism. The sacrificial coating is designed to oxidize preferentially when openings occur, transforming the harmful effect of coating breakdown into a beneficial protection system that activates precisely when needed.
Solution Approach 2:
The sacrificial coating is applied in advance to the core material before bonding occurs. This preliminary protective layer is positioned and prepared beforehand to immediately protect the core material from oxidation should stress-induced openings occur during the bonding process or subsequent handling.
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 configuration effectively reduces the oxidation of the core material, maintaining electrical performance and preventing corrosion by allowing the sacrificial layer to oxidize instead of the core material, even under stress conditions that would otherwise expose the core.
Implementation Method 1
the sacrificial layer oxidizes preferentially to reduce exposure of the core material to oxidation
Data Source
AI summary
A semiconductor device includes a bond formed on a bond pad. The bond is formed of a wire that includes a central core of conductive metal, a first coating over the central core of conductive metal that is more chemically active than the conductive metal, and a second coating over the central core of conductive metal that is less chemically active than the central core of conductive metal.