Copper Electroplating Additive for Cobalt Seed Corrosion
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Solution Overview
Problem
Conventional copper electroplating techniques face challenges in achieving voidless and seamless filling of nanometer-scale features with cobalt seed layers, particularly due to corrosion issues and the need for sophisticated additives in acidic baths with bromide ions.
Innovation Solution
An acidic aqueous copper electroplating composition comprising copper ions, bromide ions, and specific polyamine-based additives that act as both suppressing agents and corrosion inhibitors, enabling bottom-up filling and reducing cobalt seed layer corrosion in features with aperture sizes of 30 nanometers or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional copper electroplating is performed on cobalt seed layers in acidic baths with bromide ions, then copper deposition occurs, but cobalt seed layer corrosion increases and voidless filling becomes difficult
Solution Approach 1:
The patent introduces a specific suppressor additive as an intermediary substance that mediates between the copper electroplating process and the cobalt seed layer. This suppressor selectively adsorbs onto the cobalt surface, forming a protective barrier that prevents direct contact between the acidic bromide-containing electrolyte and the cobalt seed layer, thereby eliminating corrosion while maintaining effective copper deposition pathways
Solution Approach 2:
The patent changes the chemical parameters of the electrolyte by introducing a suppressor additive that modifies the electrochemical environment. The suppressor alters the adsorption characteristics and electrochemical potential at the cobalt surface, creating conditions that favor copper deposition while suppressing cobalt dissolution, thus resolving the corrosion issue without sacrificing plating effectiveness
2Productivity
If aperture sizes are reduced to below 5 nanometers, then higher integration density is achieved, but voidless and seamless copper filling becomes increasingly difficult
Solution Approach 1:
The patent applies local quality by using a suppressor additive that provides spatially selective adsorption on the feature walls. The suppressor creates localized suppression zones on the aperture walls while leaving the bottom and top regions more accessible to copper ions, enabling controlled bottom-up filling that ensures voidless and seamless copper deposition even in sub-5nm apertures
Solution Approach 2:
The suppressor additive performs preliminary action by pre-adsorbing onto the aperture walls before copper deposition begins. This pre-conditioning of the surface establishes the necessary suppression pattern that guides subsequent copper ion transport and deposition, ensuring uniform wall coverage and preventing void formation from the outset of the electroplating process
3Manufacturing precision
If suppressor additives are used to achieve bottom-up filling, then voidless filling improves, but the complexity of additive selection increases due to bromide ion interactions
Solution Approach 1:
The patent uses a suppressor additive with a molecular structure that copies or mimics the desired adsorption behavior on cobalt surfaces in the presence of bromide ions. The suppressor's functional groups are designed to replicate the selective surface interaction pattern needed for effective bottom-up filling, providing a reliable and reproducible solution that simplifies additive selection despite the complex bromide-containing electrolyte environment
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 composition effectively fills recessed features without voids or seams, providing excellent nucleation and corrosion protection for cobalt seed layers, even in small apertures, enhancing the reliability of copper electroplating processes.
Implementation Method 1
an acidic aqueous composition for copper electroplating comprising (a) copper ions; (b) bromide ions; and (c) at least one additive of formula S1
Implementation Method 2
The suppressing agents according to the present invention are particularly useful for filling of small recessed features
Implementation Method 3
The additive provides a good nucleation of copper on the cobalt seed layer. It allows electroplating over thin seed layers and fast bottom-up fill in both large and small features without causing voids or seams. Furthermore, the additive effectively suppresses corrosion of the cobalt seed layer.
Data Source
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AI summary
The present invention provides an acidic aqueous composition for copper electroplating comprising (a) copper ions; (b) bromide ions; and (c) at least one additive of formula (S1) wherein XS1 is selected from a linear, branched or cyclic C1-C12 alkanediyl, which may be substituted or unsubstituted, and which may optionally be interrupted by O, S or NRS40; RS1 is a monovalent (a) poly(oxy(C3 to C6 )alkylene)-block-poly(oxyethylene) group which is bound to the N-atom by the poly(oxy(C3 to C6 )alkylene part, or (b) a poly(oxyethylene)-block-poly(oxy(C3 to C6)alkylene)-block-poly(oxyethylene), which both have a poly(oxyethylene) content of from 5 to 30 % by weight; RS2, RS3, RS4 (a) are selected from H, RS1, RS40, or (b) RS3 and an adjacent group RS4 or, if n>2, two adjacent groups RS4 may together form a divalent group XS3; RS40 is selected from (a) linear or branched C1-C20 alkyl, which may optionally be substituted by hydroxy, alkoxy or alkoxycarbonyl, and (b) linear or branched C1-C20 alkenyl, which may optionally be substituted by hydroxyl, alkoxy or alkoxycarbonyl; XS3 is selected from a linear, branched or cyclic C1-C12 alkanediyl, which may be substituted or unsubstituted, and which may optionally be interrupted by O, S or NRS40; and n is an integer of from 1 to 6.