Non-Gold Wire Bonding via Oxide Removal and Alloy Layer Formation
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Solution Overview
Problem
The use of non-gold conductive wires in semiconductor devices can lead to bonding failures due to natural oxide films on electrode pads, and methods involving gold-based conductive films are costly and not preferred for reducing semiconductor device costs.
Innovation Solution
A manufacturing method that involves removing natural oxide films from semiconductor chip electrode pads and forming a pad-cover film with a conductive material like chromium or tungsten, which has a body-centered cubic or hexagonal close-packed crystal structure, allowing non-gold wires to form alloy layers with the pads for reliable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If non-gold conductive wires are used to reduce cost, then manufacturing cost decreases, but bonding reliability deteriorates due to oxide film interference
Solution Approach 1:
The patent applies preliminary action by removing the natural oxide film from the electrode pad surface before wire bonding occurs. This pre-treatment step ensures that when non-gold wires are bonded to the pad, they form reliable alloy layers without interference from oxide films, thus maintaining bonding reliability while using cost-effective non-gold materials
Solution Approach 2:
The patent introduces an intermediary substance (conductive paste or flux) that facilitates bonding between non-gold wires and electrode pads. This intermediary helps overcome the bonding difficulty caused by oxide films by creating a reliable metallurgical bond, enabling cost reduction through non-gold wire usage while maintaining bonding reliability
2Reliability
If gold-based conductive films are formed on electrode pads to ensure bonding reliability, then bonding reliability improves, but manufacturing cost increases
Solution Approach 1:
The patent extracts the essential function of gold-based conductive films (providing a reliable bonding surface) and replaces it with non-gold materials combined with oxide film removal and conductive paste application. This eliminates the need for expensive gold plating while maintaining the bonding reliability function through alternative means
Solution Approach 2:
The patent replaces expensive gold-based conductive films with cheaper non-gold conductive materials (such as copper or aluminum wires with conductive paste). Although these materials require more careful handling regarding oxide films, they provide cost-effective alternatives that achieve reliable bonding when combined with proper surface preparation techniques
3Reliability
If natural oxide films are removed from electrode pads to enable non-gold wire bonding, then bonding reliability improves, but additional processing steps are required
Solution Approach 1:
The patent merges the oxide film removal step with the wire bonding process by applying conductive paste or flux that simultaneously removes oxides and facilitates bonding. This combination approach reduces process complexity by integrating multiple functions into a single step or closely coupled sequence, maintaining bonding reliability while minimizing additional processing complexity
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 method reduces semiconductor device costs while ensuring bonding reliability by forming alloy layers between non-gold wires and electrode pads, enhancing electrical properties and reducing the risk of bonding failures.
Implementation Method 1
forming an alloy layer at the interface between the wire and the electrode pad
Implementation Method 2
removing a natural oxide film formed on the surface of the electrode pad
Data Source
AI summary
A manufacturing method of a BGA, includes the steps of: providing a semiconductor chip having electrode pads; and removing a natural oxide film formed on the surface of each of the electrode pads. Further, a first film comprised of a conductive member is formed on the surface of the electrode pad exposed by removing the natural oxide film, a wire is connected with the first film, and part of the wire is brought into contact with the electrode pad to form an alloy layer at the interface between the wire and the electrode pad. The crystal structure of the first film is comprised of a body-centered cubic lattice or a hexagonal close-packed lattice. The cost of the semiconductor device can be reduced while the bonding reliability of wire bonding of the semiconductor device is ensured.