Copper Electroplating Uniformity via Current Density Ratio
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Solution Overview
Problem
Current copper electroplating methods face challenges in achieving uniform deposition and high-deposition rates without compromising film quality, particularly in the context of interconnects for ICs and solar cells, where existing solutions either result in dendrite growth or are costly and hazardous.
Innovation Solution
The method involves forming an electrochemical cell with a high-surface area anode and a substrate cathode, using a suppressor agent in the electroplating solution to maintain a cathode-to-anode current density ratio of at least 20, and optionally forming a porous anodic film on the anode to promote uniform electrical double layers, enabling high-quality copper deposition at rates exceeding 6 μm per minute.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If alkaline copper electroplating solutions are used to achieve high-throwing power, then uniform deposition is improved, but deposition rate decreases and film quality deteriorates due to dendrite growth
Solution Approach 1:
The patent changes the pH parameter from alkaline to acidic range, and adjusts copper ion concentration to 50-150 g/L, achieving both high throwing power for uniform deposition and high deposition rates up to 10 μm/min without dendrite formation
Solution Approach 2:
The patent uses a composite electroplating solution containing sulfuric acid, copper sulfate, and organic additives (accelerators and levelers) that work synergistically to achieve both uniform deposition and high deposition rates
2Productivity
If copper electroplating is performed at high deposition rates, then productivity is improved, but film quality deteriorates due to dendrite growth
Solution Approach 1:
The patent optimizes current density to 100-500 A/m² in the acidic electroplating solution, enabling high deposition rates while maintaining film uniformity and preventing dendrite formation through controlled electrochemical reactions
Solution Approach 2:
The patent employs leveler additives that provide feedback control during electroplating, automatically adjusting deposition rate across the substrate surface to maintain uniform film quality even at high overall deposition rates
3Productivity
If fluoroborate electroplating solutions are used to achieve high-speed deposition, then productivity is improved, but cost increases and environmental hazards increase
Solution Approach 1:
The patent uses inexpensive, non-hazardous sulfuric acid-based electroplating solution that can be easily prepared and disposed of, replacing expensive and hazardous fluoroborate solutions while maintaining high deposition rates
Solution Approach 2:
The patent converts the typically problematic acidic environment into a benefit by using sulfuric acid to achieve both high deposition rates and excellent throwing power, eliminating the need for expensive fluoroborate chemistry
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 copper films that are substantially free of dendrites, exhibit a high-degree of (111) crystallographic texture, and are deposited at high rates, enhancing the performance and efficiency of copper interconnects in ICs and solar cells while minimizing environmental impact.
Implementation Method 1
The substrate functions as a cathode of an electrochemical cell in which the electroplating solution functions as an electrolyte, and the copper from the electroplating solution or a consumable anode is electroplated into the trench responsive to a voltage applied between the substrate and an anode
Implementation Method 2
copper from the electroplating solution or a consumable anode is electroplated into the trench responsive to a voltage applied between the substrate and an anode
Implementation Method 3
forming a porous anodic film on the anode to promote uniform electrical double layers
Data Source
AI summary
Embodiments of the invention are directed to methods of electroplating copper onto at least one surface of a substrate in which more uniform electrical double layers are formed adjacent to the at least one surface being electroplated (i.e., the cathode) and an anode of an electrochemical cell, respectively. In one embodiment, the electroplated copper may be substantially-free of dendrites, exhibit a high-degree of (111) crystallographic texture, and/or be electroplated at a high-deposition rate (e.g., about 6 μm per minute or more) by electroplating the copper under conditions in which a ratio of a cathode current density at the at least one surface to an anode current density at an anode is at least about 20. In another embodiment, a porous anodic film may be formed on a consumable copper anode using a long conditioning process that promotes forming a more uniform electrical double layer adjacent to the anode.