Polymeric Leveling Agents for Uniform Copper Electroplating
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Solution Overview
Problem
The challenge in copper electroplating is achieving uniform metal deposits on substrates with irregular topography, particularly in wide metal lines, which often results in stress-induced voiding and increased resistivity, leading to early electro-migration failure in electronic devices.
Innovation Solution
A copper electroplating composition incorporating a polymeric leveling agent with ethyleneically unsaturated nitrogen-containing heterocyclic monomers, along with optional accelerators, suppressors, and halide ions, is used to selectively incorporate impurities into the metal deposits, reducing stress-induced voiding and achieving uniform thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electroplating compositions are used to plate substrates with irregular topography, then the plating process is simple, but the metal deposit becomes uneven with overplating on surface irregularities
Solution Approach 1:
The patent modifies the chemical parameters of the plating composition by introducing specific leveling agents (polyacrylamide, polyethylene oxide, polyoxyalkylene amines) and suppressors (polyethers, polyoxyalkylene block copolymers) in controlled concentrations. These parameter changes enable the composition to achieve uniform metal deposit thickness across irregular surfaces by controlling the electroplating rate at different locations on the substrate.
Solution Approach 2:
The patent employs intermediary substances (leveling agents and suppressors) that mediate between the electroplating process and the substrate topography. These intermediaries selectively adsorb at different rates on surface irregularities, controlling local current density and metal deposition to achieve uniform thickness despite underlying surface variations.
2Reliability
If higher purity copper is used in wide metal lines, then resistivity is reduced, but stress-induced voiding increases in dual damascene structures
Solution Approach 1:
The patent applies local quality by using selective impurity incorporation strategies where different impurity levels are introduced in different regions. Wide metal lines receive higher impurity levels (50-500 ppm) to suppress voiding, while narrow interconnect lines maintain lower impurity levels (<50 ppm) for high conductivity. This spatial variation in impurity concentration resolves the contradiction between voiding suppression and resistivity control.
Solution Approach 2:
The patent changes the compositional parameters of the copper deposit by controlling impurity content through selective electroplating conditions. By adjusting plating parameters (current density, temperature, composition) and using specific additives, the patent achieves different impurity levels in different metal line regions, optimizing both voiding resistance and electrical conductivity for their respective locations.
3Object-generated harmful factors
If impurities are selectively incorporated into wide metal lines, then stress-induced voiding is reduced, but resistivity increases
Solution Approach 1:
The patent implements local quality by spatially differentiating impurity incorporation based on metal line width. Wide metal lines (greater than 5 micrometers) receive higher impurity concentrations (50-500 ppm) to suppress stress-induced voiding, while narrow interconnect lines (less than 5 micrometers) maintain lower impurity concentrations (<50 ppm) to preserve electrical conductivity. This localized approach resolves the contradiction by matching impurity levels to the specific functional requirements of each region.
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 provides substantially planar metal deposits with reduced void formation and controlled impurity levels, enhancing the reliability and longevity of electronic devices by minimizing resistivity and voiding in wide metal lines.
Implementation Method 1
Methods for electroplating articles with metal such as copper generally involve passing a current between two electrodes in a plating solution where one of the electrodes is the article to be plated (typically the cathode)
Data Source
AI summary
Leveling agents for metal plating baths are provided. Plating baths containing such leveling agents provide metal deposits having substantially level surfaces. Such leveling agents may be selected to selectively incorporate desired levels of impurities into the metal deposit.