Electroless Cobalt Deposition Using Ti3+ Reducing Agent
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Solution Overview
Problem
Existing electroless plating methods for depositing cobalt in semiconductor devices face challenges such as non-homogeneous nucleation, environmental concerns due to hydrogen-containing reducing agents like hydrazine, and operational limitations at high temperatures and pH levels, which affect the purity and continuity of the cobalt film.
Innovation Solution
The use of Ti3+ ions as a reducing agent in an electroless deposition process, combined with Co2+ ions, provides a more environmentally friendly and stable solution that operates at room temperature and lower pH, eliminating gas evolution and enabling the deposition of a smooth, continuous cobalt film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If hydrazine or hydrogen-containing compounds are used as reducing agents, then cobalt can be deposited, but environmental concerns arise and H2 gas is incorporated in the deposit affecting purity
Solution Approach 1:
Ti3+ ions are introduced as an intermediary reducing agent that mediates the reduction of Co2+ to Co metal. The Ti3+ ions are oxidized to Ti4+ during the process, eliminating the need for hydrazine or other hydrogen-containing reducing agents that cause environmental pollution and gas incorporation in the deposit.
2Quantity of substance
If traditional electroless plating methods are used, then cobalt deposition is achieved, but non-homogeneous nucleation occurs affecting film continuity
Solution Approach 1:
The oxidation potential of the reducing agent is changed from hydrazine to Ti3+ ions. This parameter change in the reducing agent's chemical properties enables homogeneous nucleation and continuous film formation, as Ti3+ provides a more controlled reduction process compared to traditional hydrogen-containing reducing agents.
3Quantity of substance
If high temperature and high pH conditions are used, then electroless deposition can proceed, but dielectric materials are damaged
Solution Approach 1:
The operating temperature and pH parameters are changed from high values to room temperature and lower pH conditions. This is achieved by using Ti3+ ions as the reducing agent, which has different kinetic and thermodynamic properties compared to traditional reducing agents, allowing the deposition to proceed under milder conditions that do not damage dielectric 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 results in a pure, continuous cobalt film suitable for semiconductor applications, reducing operational costs and complexity, and allowing for the formation of thin cobalt layers without the need for plasma etching, while being environmentally friendlier and more stable than hydrazine-based electrolytes.
Implementation Method 1
electroless deposition of cobalt is accomplished using hydrazine or other hydrogen containing compounds as reducing agents
Implementation Method 2
Ti3+ ions as a reducing agent in an electroless deposition process, combined with Co2+ ions
Data Source
AI summary
A solution for electroless deposition of cobalt is provided. A reducing agent of Ti3+ ions is provided to the solution. Co2+ ions are provided to the solution.