Basic Copper Alloy Electrolyte for Thin Damascene Barrier Layers
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Solution Overview
Problem
The Damascene process for creating conductive interconnects in integrated circuits faces challenges such as non-uniform thickness of deposited layers, contamination issues from acidic copper electrodeposition compositions, and the need for thick barrier layers which occupy valuable space in small structures.
Innovation Solution
An electrolyte with a pH greater than 6, containing copper (II) ions, an organic zinc (II) or manganese (II) salt, and diethyleneamine, is used for the electrodeposition of a copper alloy. This electrolyte allows for the deposition of thin, uniform copper layers with low impurity content, and enables the formation of a diffusion barrier layer without the need for a separate barrier material deposition step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If acidic copper electrodeposition compositions are used, then copper deposition efficiency is improved, but contaminant generation (carbon, chlorine, sulfur) increases causing reliability and current leakage problems
Solution Approach 1:
The invention changes the pH parameter from acidic to basic (pH > 6), which fundamentally alters the deposition chemistry. This parameter change eliminates the generation of harmful contaminants (carbon, chlorine, sulfur) while maintaining copper deposition efficiency, as the basic electrolyte composition prevents these byproducts from forming during the electrodeposition process.
2Productivity
If PVD or CVD processes are used for copper deposition, then deposition speed is improved, but layer thickness uniformity deteriorates (thicker on protruding parts, thinner in hollows)
Solution Approach 1:
The invention replaces physical vapor deposition (PVD) or chemical vapor deposition (CVD) with electrodeposition. This substitution changes the deposition mechanism from a physical/chemical vapor process to an electrochemical process that uses ionic conduction in a basic electrolyte. The electrochemical mechanism enables uniform copper deposition in hollows and on protruding parts while maintaining high deposition speed, eliminating the thickness uniformity problems inherent in PVD/CVD methods.
3Reliability
If thick barrier layers are deposited to prevent copper migration, then diffusion prevention is improved, but available copper volume in small structures is reduced
Solution Approach 1:
The invention changes the pH parameter to basic (pH > 6) and uses a basic copper electrolyte composition that enables direct electrodeposition of copper with inherent diffusion barrier properties. This parameter change eliminates the need for thick separate barrier layers, as the basic electrolyte process produces copper deposits that are less prone to migration, thereby maximizing the available copper volume in small structures while maintaining diffusion prevention.
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 proposed solution enables the deposition of thin, uniform copper layers with low impurity content, reduces the thickness or eliminates the need for barrier layers, and enhances the reliability and performance of electronic devices by minimizing contaminants and maximizing copper volume in small structures.
Implementation Method 1
an electrolyte for the electrodeposition of an alloy of copper and a metal selected from manganese and zinc
Implementation Method 2
copper (II) ions in a molar concentration being between 1 mM and 120 mM
Implementation Method 3
The doping element, uniformly distributed in the deposited film, has the particular feature of migrating to one or more interfaces during a subsequent annealing step
Implementation Method 4
The doping element has the particular feature of forming a barrier to the diffusion of copper for example, by aggregating with another metal (titanium or tantalum for example) or at the silicon oxide-metal interface
Data Source
AI summary
The present invention relates to an electrolyte and its use in a process for fabricating copper interconnects. The electrolyte of pH greater than 6.0 comprises copper ions, manganese or zinc ions, and ethylenediamine which complexes the copper. A thin barrier layer is formed by annealing the deposited copper alloy, which causes manganese or zinc to migrate to the interface between the insulating dielectric material and the copper.