Electroless Plating Chamber with Acidic Copper Solution
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Solution Overview
Problem
Conventional electroless copper deposition processes face challenges with alkaline pH solutions, including non-compatibility with positive photoresist, longer induction times, decreased nucleation density, and adhesion issues on certain substrate surfaces like tantalum nitride, which are exacerbated by oxidation in alkaline environments.
Innovation Solution
A chamber and acidic pH electroless copper plating solution formulation using a copper(II) salt, cobalt(II) salt, polyamine-based complexing agent, and chemical brightener, with de-oxygenated liquids to prevent oxidation, allowing for improved adhesion and nucleation density on substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If highly alkaline pH electroless plating solution is used, then deposition rate is enhanced, but adhesion to substrate and compatibility with photoresist deteriorates
Solution Approach 1:
The patent changes the pH parameter from highly alkaline (pH>9) to mildly alkaline (pH 8.0-8.5), which resolves the contradiction by maintaining sufficient deposition rate while eliminating hydroxylation inhibition and improving adhesion to substrates like tantalum nitride
Solution Approach 2:
The patent introduces an inert atmosphere (nitrogen or argon) environment during electroless plating to prevent oxidation of the copper interface, which eliminates the need for highly alkaline conditions and improves both adhesion and photoresist compatibility
2Productivity
If highly alkaline pH electroless plating solution is used, then deposition rate is enhanced, but induction time increases
Solution Approach 1:
The patent optimizes the pH parameter to mildly alkaline (pH 8.0-8.5) and adjusts metal ion concentrations (copper: 0.01-0.1M, cobalt: 0.01-0.05M) to achieve fast deposition rates without prolonged induction periods, eliminating the time loss associated with highly alkaline solutions
3Productivity
If highly alkaline pH electroless plating solution is used, then deposition rate is enhanced, but nucleation density decreases
Solution Approach 1:
The patent changes the pH parameter to mildly alkaline (pH 8.0-8.5) and optimizes metal ion concentrations to promote high nucleation density, eliminating the hydroxylation inhibition that causes large grain growth and low nucleation density in highly alkaline environments
Solution Approach 2:
The patent uses a composite plating solution containing multiple metal ions (copper and cobalt) that work synergistically to achieve both high deposition rate and high nucleation density, avoiding the trade-off present in single-component highly alkaline solutions
4Reliability
If de-oxygenated liquids are used, then adhesion and nucleation density are enhanced, but process complexity increases
Solution Approach 1:
The patent implements a simple inert atmosphere (nitrogen or argon) environment that prevents oxidation without requiring complex de-oxygenation equipment, achieving improved adhesion while maintaining process simplicity
Solution Approach 2:
The patent uses inert gas as an intermediary medium to prevent oxidation of the copper interface, providing a simple and effective solution that avoids complex de-oxygenation procedures while achieving the desired adhesion improvement
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 solution enables efficient electroless copper deposition with enhanced adhesion and nucleation density, reducing line resistance and allowing the use of standard positive resist photomask materials, while maintaining a controlled environment to prevent oxidation.
Implementation Method 1
During electroless copper deposition, electrons are transferred from a reducing agent to the copper ions resulting in the deposition of reduced copper onto the wafer surface
Implementation Method 2
de-oxygenated liquids to prevent oxidation
Data Source
AI summary
An electroless plating chamber is provided. The electroless plating chamber includes a chuck configured to support a substrate and a bowl surrounding a base and a sidewall of the chuck. The base has an annular channel defined along an inner diameter of the base. The chamber includes a drain connected to the annular channel. The drain is capable of removing fluid collected from the chuck. A proximity head capable of cleaning and substantially drying the substrate is included in the chamber. A method for performing an electroless plating operation is also provided.