In the relentless pursuit of precision and efficiency within semiconductor manufacturing, a groundbreaking advancement has emerged from the laboratories of Xiamen University in China. Addressing a long-standing challenge in the monitoring of critical chemical additives, a team of researchers has developed an innovative electrochemical microfluidic workstation specifically designed for the real-time, onsite detection of additive concentrations in acidic copper plating solutions. This breakthrough technology promises to revolutionize quality control protocols by enabling rapid, accurate, and low-volume analysis that is crucial for maintaining the stability and reliability of metal interconnections in integrated circuit fabrication.
Traditional methodologies for measuring additive concentrations in acidic copper plating baths predominantly utilize bulky platinum rotating disk electrodes with diameters ranging from two to three millimeters. Though effective in certain contexts, these systems demand large volumes of plating solution to sustain unrestricted electrolyte flow at high rotational speeds. This requirement poses significant practical limitations — from cumbersome operational workflows to the stifling of miniaturization efforts that could enhance portability and automation. The dependence on complex mechanical rotation apparatus also significantly inflates system costs and maintenance complexities.
To surmount these impediments, the research collective harnessed the power of microfluidics combined with ultramicroelectrodes. The crux of their design centers on utilizing static platinum ultramicroelectrodes, typically an order of magnitude smaller than conventional rotating disk electrodes. This notable miniaturization reduces capacitance effects and effectively eliminates IR drop concerns while accelerating the mass transfer of analytes to the sensor surface. These characteristics yield superior signal-to-noise ratios, directly enhancing measurement sensitivity and accuracy. The shift from rotating to static electrodes also simplifies the mechanical design, enabling a more compact, cost-effective, and robust analytical device.
The researchers embraced cutting-edge 3D printing techniques to fabricate molds for the microfluidic chip, epitomizing the fusion of advanced manufacturing methods with analytical chemistry. By casting polydimethylsiloxane (PDMS) prepolymer into these 3D-printed molds and subjecting the assemblies to thermal curing processes, the team crafted bespoke microfluidic chambers perfectly tailored for fluid manipulation and interfacing with ultramicroelectrodes. Subsequent precise physical drilling and oxygen plasma bonding ensured airtight seals and structural integrity essential for reliable fluid handling and electrochemical analysis.
One hallmark of this system’s ingenuity is its programmed microfluidic mixing capability. By controlling fluid dynamics at the microscale, the workstation achieves homogeneous sample preparation and efficient interaction between plating solution additives and the sensor surface. This integration culminates in a drastic reduction of the required solution volume to a mere 220 microliters per test—minuscule compared to conventional systems. Such economy not only conserves valuable chemical resources but also streamlines sampling protocols, paving the way for high-throughput, automated quality control.
Calibration strategies were meticulously developed based on the additive-induced modulation of copper deposition kinetics—a mechanistic approach that anchors analytical accuracy in fundamental electrochemical behavior. Employing these calibration curves, the system quantifies suppressors, accelerators, and levelers with an impressive average relative error below 10%. These precision metrics meet the stringent demands of semiconductor manufacturing lines, where even minor deviations in additive concentration can precipitate catastrophic device failures or yield losses.
Beyond the technical virtues, the electrochemical microfluidic workstation embodies a visionary metaphor: a ‘Fitness Tracker’ for acidic copper plating solutions. As articulated by Associate Professor Lianhuan Han, the device empowers continuous, real-time monitoring of additive concentrations, furnishing manufacturers with immediate feedback akin to health metrics in wearable electronics. This continuous surveillance capability can preempt process instabilities, optimize additive dosing, and ultimately enhance the robustness and repeatability of copper plating processes critical for reliable metal interconnections.
Historically, detection instruments based on rotary electrodes have been burdened by the necessity for dedicated rotators and speed controllers, introducing mechanical complexity, increased power consumption, and potential points of failure. The new static ultramicroelectrode-based design eliminates these dependencies, facilitating streamlined instrument architecture amenable to miniaturization and field deployment. This attribute could catalyze a paradigm shift toward portable, user-friendly sensors adaptable across diverse manufacturing environments.
The underlying electrochemical principles leveraged in this workstation harness the advantages of ultramicroelectrodes such as reduced double-layer capacitance and enhanced mass transfer facilitated by radial diffusion. These aspects contribute to faster response times and higher sensitivity, capacities paramount when detecting sub-millimolar concentrations of organic additives regulating copper deposition. Moreover, the compact sensor footprint synergizes with microfluidic volumetric control to minimize waste generation and environmental impact—an increasingly vital consideration in sustainable industrial chemistry.
Looking forward, the research team envisions extending this technology platform beyond the semiconductor domain. The modularity and adaptability of the electrochemical microfluidic workstation lend themselves to monitoring various chemical additives across disparate industries—from electroplating in automotive manufacturing to biochemical assays in environmental monitoring. Such versatility could transform current sensing paradigms, placing precise, online chemical diagnostics within reach of numerous industrial sectors.
Scaling from laboratory prototypes to industrial-scale implementations remains a focal point for future investigations. Challenges inherent to real-world deployment, such as sensor fouling, long-term stability, and integration with process control systems, will require innovative engineering and robust validation. Nonetheless, the foundational work lays a compelling blueprint that melds advanced manufacturing techniques, electrochemical ingenuity, and microfluidic precision into an analytical powerhouse.
In summary, this pioneering electrochemical microfluidic workstation marks a substantial leap forward in on-line additive concentration detection for acidic copper plating solutions. By overcoming the limitations of traditional electrode designs and leveraging the synergies of microfluidics and ultramicroelectrodes, the system promises enhanced accuracy, reduced reagent consumption, and operational simplicity. Its deployment is poised to enhance process control in integrated circuit metal interconnect fabrication, contributing to the production of more reliable, high-performance semiconductors. This innovation quintessentially embodies the fusion of materials science, electrochemistry, and microengineering driving the next frontier in industrial manufacturing technology.
Subject of Research: Not applicable
Article Title: On-line detection of additive concentrations in acidic copper plating solution for metal interconnection by an electrochemical microfluidic workstation
News Publication Date: 26-Jun-2025
Web References:
https://www.rsc.org/journals-books-databases/about-journals/industrial-chemistry-materials/
http://dx.doi.org/10.1039/D5IM00073D
References:
Han, Lianhuan et al. “On-line detection of additive concentrations in acidic copper plating solution for metal interconnection by an electrochemical microfluidic workstation.” Industrial Chemistry & Materials, 26 June 2025. DOI: 10.1039/D5IM00073D
Image Credits:
Bo Zhang, Fang-Zu Yang, Dongping Zhan, and Lianhuan Han, Xiamen University, China.
Keywords
Electrochemical detection, Microfluidics, Ultramicroelectrodes, Copper plating, Additive concentration, Integrated circuits, Semiconductor manufacturing, On-line monitoring, 3D printing, Process control, Metal interconnection, Industrial chemistry
