Low-Copper Electroplating for Damascene Fill Defect Control
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Solution Overview
Problem
Conventional copper electroplating solutions face challenges in achieving uniform and reproducible fill of submicron damascene features due to seed layer dissolution and rapid deposition rates, leading to defects and voids, especially with thinner seed layers and smaller feature sizes.
Innovation Solution
A low-copper, low-acid electrolyte with a suppressor compound and organic additives is used, inducing a high overpotential to protect the seed layer and allow for a slow plating process, enabling a bottom-up fill mechanism with reduced current density and increased plating time to prevent defects and ensure uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional copper electroplating solutions are used with standard copper concentrations, then deposition rate is maintained, but seed layer dissolution occurs and fill uniformity deteriorates
Solution Approach 1:
The patent changes the copper ion concentration parameter from conventional levels (typically 20-50 g/L) to a low copper concentration range (0.1-10 g/L). This parameter change fundamentally alters the plating mechanism, enabling slower deposition rates that allow organic additives sufficient time to adsorb and direct bottom-up fill, thereby achieving uniform fill without seed layer dissolution while maintaining acceptable productivity
Solution Approach 2:
The patent employs preliminary action by pre-adsorbing organic additives (suppressors and accelerators) onto the substrate surface before significant copper deposition occurs. The low copper concentration enables this preliminary adsorption phase, where suppressors preferentially adsorb on protruding regions and accelerators on recessed regions, establishing the conditions for uniform bottom-up fill before the deposition bulk phase begins
2Reliability
If strong suppressor is used to protect seed layer, then seed layer protection improves, but suppressor agglomeration causes streaks and defects
Solution Approach 1:
The patent changes the suppressor concentration parameter and its interaction with copper ion concentration. By operating at low copper concentrations, the suppressor remains in solution at effective protective levels without reaching the agglomeration threshold. The low copper environment prevents suppressor precipitation and agglomeration that would otherwise cause visible streaks and deposition defects, enabling continuous seed layer protection throughout the plating process
Solution Approach 2:
The patent introduces organic additives as intermediary substances that mediate between the copper ions and the seed layer. These intermediaries (suppressors and accelerators) adsorb onto the substrate surface and modulate copper deposition behavior, providing gentle, uniform protection to the seed layer while directing copper to fill recessed regions, thereby avoiding the harsh effects of strong suppressor concentrations
3Productivity
If rapid deposition is used to maintain productivity, then output increases, but voids and defects increase
Solution Approach 1:
The patent implements periodic action by dividing the plating process into distinct phases: an initial phase with very low copper concentration allowing additive adsorption and nucleation, followed by a main deposition phase at slightly higher but still low copper concentration. This periodic variation in copper availability enables controlled, defect-free fill during the initial phase while maintaining acceptable deposition rates during the main phase, achieving both quality and productivity
Solution Approach 2:
The patent uses preliminary action by allowing organic additives to adsorb and establish a controlled deposition environment before rapid deposition begins. The low copper concentration during the preliminary phase ensures uniform additive distribution and proper nucleation sites are formed, preventing void formation during subsequent faster deposition phases, thus enabling higher overall throughput without sacrificing fill quality
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 method achieves a more uniform and reproducible copper fill of submicron features with fewer defects, protecting the seed layer and promoting high nucleation density, resulting in a continuous copper film without sidewall voids.
Implementation Method 1
the low copper electrolyte induces a cathodic overpotential on the seed sufficient to protect the seed from dissolution by acid in the electrolyte during immersion
Implementation Method 2
electroplating copper into the features at a current density of about 3 mA/cm2 or less
Implementation Method 3
allowing for a slow, uniform deposition process, allowing for a bottom-up fill mechanism and reducing defects
Data Source
AI summary
Certain embodiments herein relate to a method of electroplating copper into damascene features using a low copper concentration electrolyte having less than about 10 g/L copper ions and about 2-15 g/L acid. Using the low copper electrolyte produces a relatively high overpotential on the plating substrate surface, allowing for a slow plating process with few fill defects. The low copper electrolyte may have a relatively high cloud point.