Copper Wire Bonding on Silver Plated Leads via Oxygen Plasma
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Solution Overview
Problem
The reliability of semiconductor devices using copper wires for wire bonding is compromised due to inhibited alloy layer formation at the interface between copper wires and pad electrodes, resulting from argon plasma treatment, which lowers connection strength and overall device reliability.
Innovation Solution
The method involves performing oxygen plasma treatment on the lead frame and semiconductor chip after die bonding, followed by a reduction treatment of the silver plating layer, allowing for effective cleaning and oxidation of the surface, thereby facilitating strong connections between copper wires and silver plating layers during wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If argon plasma treatment is performed on the lead frame and semiconductor chip, then the surface is cleaned and oxidation is prevented, but the alloy layer formation at the interface between copper wires and pad electrodes is inhibited, resulting in lower connection strength
Solution Approach 1:
The patent applies preliminary oxidation treatment to the pad electrode surface before wire bonding. By intentionally forming a thin oxide layer on the pad electrode surface in advance, the surface becomes more reactive and promotes alloy layer formation when copper wires are bonded, thereby improving connection strength while maintaining the benefits of plasma cleaning.
Solution Approach 2:
The patent changes the chemical state of the pad electrode surface by controlling oxidation. By adjusting oxidation conditions (temperature, time, atmosphere) to form a specific thickness of oxide layer, the surface properties are optimized to enhance alloying during wire bonding without excessive oxidation that would harm connection strength.
2Reliability
If copper wires are used for wire bonding, then cost is reduced compared to gold wires, but reliability is compromised due to inhibited alloy layer formation
Solution Approach 1:
The patent prepares the pad electrode surface in advance by controlled oxidation to enhance its reactivity. This preliminary action ensures that when copper wires are bonded, alloy layers form effectively, improving connection reliability while maintaining the cost advantage of using copper instead of gold wires.
Solution Approach 2:
The patent optimizes the chemical parameters of the pad electrode surface through controlled oxidation. By adjusting oxidation conditions to create an optimal oxide layer thickness, the surface becomes more compatible with copper wire bonding, thereby improving reliability while maintaining ease of manufacture with copper materials.
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 alloying rate and connection strength between copper wires and pad electrodes, improving the reliability of the semiconductor device by ensuring clean metal surfaces for bonding and preventing the formation of oxide layers that hinder the bonding process.
Implementation Method 1
performing oxygen plasma treatment on the lead frame and the semiconductor chip after the process (b)
Implementation Method 2
reducing the surface of the silver plating layer after the step (c)
Data Source
AI summary
After a die bonding step, a wire bonding step is performed to electrically connect the plurality of pad electrodes and the plurality of leads of the semiconductor chip via a plurality of copper wires. A plating layer is formed on a surface of the lead, and a copper wire is connected to the plating layer in the wire bonding step. The plating layer is a silver plating layer. After the die bonding step, an oxygen plasma treatment is performed on the lead frame and the semiconductor chip before the wire bonding step, and then the surface of the plating layer is reduced.