Copper Pillar Oxidation Prevention via Self-Assembled Monolayer
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Solution Overview
Problem
Copper pillar bumps in integrated circuit fabrication face challenges due to poor adhesion caused by oxidation, leading to reliability concerns and potential underfill cracking.
Innovation Solution
A method involving the formation of a passivation layer, a metal pillar, and a solder layer, with the sidewalls of the metal pillar reacting with an organic compound to form a self-assembled monolayer or multi-layers, providing protection against oxidation and improving adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper pillar bumps are used to achieve finer pitch and reduce capacitance load, then circuit performance is improved, but oxidation of copper pillar causes poor adhesion and reliability concerns
Solution Approach 1:
An organic compound layer is introduced as an intermediary between the copper pillar and the external environment. This organic compound self-assembles on the copper surface to form a protective monolayer or multi-layer structure that acts as a barrier against oxidation, while maintaining adhesion properties for subsequent bonding processes
Solution Approach 2:
The organic compound creates an inert protective environment around the copper pillar surface through self-assembly. This molecular barrier effectively isolates the reactive copper surface from oxygen exposure during storage and processing, preventing oxidation without requiring external inert gas atmospheres throughout the entire fabrication process
2Reliability
If copper pillar bumps are used to reduce capacitance load and enable higher frequencies, then circuit performance is improved, but poor adhesion due to oxidation leads to potential underfill cracking
Solution Approach 1:
The organic compound layer serves as a mediator that prevents the chain reaction from oxidation to poor adhesion to underfill cracking. By forming a protective barrier on the copper pillar surface, it ensures proper adhesion that can withstand the mechanical stresses of underfilling and subsequent thermal cycling
Solution Approach 2:
The organic compound is applied in advance to the copper pillar surface before underfilling and final assembly. This preliminary protective action ensures that the copper pillar maintains its adhesion properties throughout subsequent processing steps, preventing underfill cracking before it can occur
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
The self-assembled monolayer or multi-layers effectively prevent oxidation of the copper pillar, enhancing the adhesion and reliability of the electronic component to the substrate, thereby improving the overall performance and reducing leakage currents.
Implementation Method 1
causing sidewalls of the metal pillar to react with an organic compound to form a self-assembled monolayer of the organic compound on the sidewalls of the metal pillar
Implementation Method 2
causing sidewalls of the metal pillar to react with an organic compound to form a self-assembled monolayer of the organic compound on the sidewalls of the metal pillar
Data Source
AI summary
The disclosure relates to fabrication of to a metal pillar. An exemplary method of fabricating a semiconductor device comprises the steps of providing a substrate having a contact pad; forming a passivation layer extending over the substrate having an opening over the contact pad; forming a metal pillar over the contact pad and a portion of the passivation layer; forming a solder layer over the metal pillar; and causing sidewalls of the metal pillar to react with an organic compound to form a self-assembled monolayer or self-assembled multi-layers of the organic compound on the sidewalls of the metal pillar.