Language
Country/Area
No result found
The mysterious "Damacin" process: How does copper perfectly fill the tiny channels?
Since IBM and Motorola first used copper in integrated circuit interconnects in 1997, this revolutionary process has continued to change the face of the semiconductor industry. Compared with aluminum, copper's superior conductivity allows many ICs to be designed with thinner wires and significantly reduces energy consumption, ultimately improving overall performance.
Copper's advantage lies not only in its conductivity, but also in its resistance to electromigration during the flow of electric current.
However, the process of switching from aluminum to copper is not easy. This requires entirely new manufacturing technologies and processes, including a complete overhaul of metal patterning methods. Previous techniques, which relied on photoresist masks and plasma etching, have not been successful for copper applications. This forced scientists to rethink the metal patterning process, ultimately developing a method called the Damascene process.
The process of Damasin craft
In the damazine process, the underlying silicon oxide insulating layer needs to be chiseled into clear grooves to determine the location of the conductors, and then the insulating layer is thickly plated with copper to exceed the required fill volume. Then, through chemical mechanical planarization (CMP) technology, the copper that is above the top of the insulating layer is removed, leaving the copper that sinks into the insulating layer as a delicate and functional conductor.
This process allowed the scientists to fill as many as ten or more metal layers in a multilayer interconnect structure, demonstrating the resilience and scalability of the Damazine process.
The role of blocking metal
Complete coverage of the barrier metal layer is critical to ensure effective use of the copper conductor. Excessive copper diffusion can lead to undesirable interactions with surrounding materials, especially the risk of copper forming deep traps in the silicon. Therefore, the barrier metal must reduce the diffusion properties of copper while maintaining good electrical contact. Thin barrier layers can lead to contact contamination, while thick layers increase overall resistance.
Challenges of Electromigration
In electronics, electromigration is the process by which a metal conductor changes shape under the influence of an electric current, which can ultimately lead to the conductor breaking. Because copper outperforms aluminum in this process, it can support higher currents through the same size wire, making it the conductor material of choice in the semiconductor industry.
With the development of technology, the application of copper materials has become more and more mature and has become the core of today's semiconductor industry.
Further development of super-conformal electrodeposition technology
As processor frequencies reached 3 GHz in the 2000s, capacitive RC coupling of interconnects became the main speed limiting factor. At this time, the choice of copper is to take into account the needs of both low impedance and low capacitance performance. The copper electroplating process is based on its attached seed layer, followed by super-conformal electrodeposition to fill the tiny channels. The different additives contained in this process also optimize the filling of copper in the channels accordingly.
Super conformity to electrodeposition model
In superconducting metal electrodeposition, there are mainly two models to explain its mechanism. The first is the curvature-enhanced adsorbent concentration model, which emphasizes the importance of accelerators in the bottom channel; the second is the S-type negative differential resistance model, which advocates that the role of inhibitors is more significant. Although their arguments are different, both emphasize the key factors to improve electrical conductivity.
Future Outlook
As the demand for semiconductor technology continues to grow, the applications of copper and related technologies are also evolving. Currently, scientists are looking for new materials and more efficient manufacturing technologies to replace the traditional copper-silicon bonding method in an attempt to overcome the current obstacles. So, how will research in this area impact the semiconductor industry in the future?
