Powerful electronics require more and more connections in ever smaller spaces. Established technologies are reaching the limits of what is physically possible. Researchers at the Fraunhofer IZM-ASSID in Dresden, together with partners, have further developed a connection technology with wires in the nm range. The new technology can be used to advantage in the industrial production of 300 mm silicon wafers.
Powerful electronics require more connections in ever smaller spaces. Established technologies are reaching the limits of what is physically possible. Researchers at the Fraunhofer IZM-ASSID in Dresden and their partners have further developed a connection technology with wires in the nm range. This new technology offers advantages in the industrial production of 300 mm silicon wafers.
Data centers have to process unimaginably large amounts of data - and not just since the AI hype. For a long time now, complicated processes have had to be processed at extremely high speeds in certain areas. The demands on computing power are constantly increasing. New connection technologies can make their contribution here: the smaller the area required for connections, the more transistors can be implemented on a given chip area. The product becomes correspondingly more powerful. Flip-chip components use copper bumps for soldered connections. Further shrinking of the structures of this technology reaches its limits where the soldering processes can no longer reliably avoid tin connections between neighboring elements.
In the search for alternatives, Prof. Dr. Iuliana Panchenko and her team at Fraunhofer IZM-ASSID decided to test new joining techniques for contacts that are shrunk to less than 10 µm. As part of the SME project 'NanoInt', funded by the Fraunhofer-Gesellschaft, she and her partners from the company NanoWired have developed a promising option based on copper nanowires and successfully tested it for use on 300 mm silicon wafers.
NanoWires can be applied to almost any material using the galvanic process; Image: NanoWired The direct connection in the form of copper nanowires has several advantages. The pluggable solution (nanowire to nanowire) means that designs with different heights can be realized. No other metallic materials need to be used, the resulting system is mechanically robust and offers the chip designer a great deal of freedom. The connections can be produced at room temperature and with only limited bonding pressure, which makes the technology resource-efficient and particularly suitable for thin or heat-sensitive chips.
Initially, the researchers concentrated on growing the nanowires at the contact points as evenly as possible across the entire 300 mm wafer. They achieved this by using special membranes with tiny pores that determine how thick the nanowire becomes. They can be varied for thicknesses from 100 nm to 1 µm. Choosing the right pore diameter is crucial to creating a reliable and well-conducting connection. As soon as the membrane is in place, a galvanic process is set in motion and the copper nanowires can grow through the pores.
To assess the practicality of the new connection technology, the researchers tested how the process can be integrated into an industrial process chain. In doing so, they defined the optimum parameters for assembling the systems and paid particular attention to reproducibility, homogeneity, mechanical robustness and the feasibility of the technology for industrial use.
The NanoWired company, the Fraunhofer IMWS and the IAVT of the Technical University of Dresden were involved in the 'NanoInt' project.
