Monday, January 1, 2018

Aveni extends copper interconnects to 5nm and below for BEOL integration employing ALD TaN & CVD Co barrier/seed

Recently at IEDM 2017 IBM announced that copper is here to stay and can continue to be scaled for the future back end of line (BEOL) interconnects - 20 Years of Cu BEOL in Manufacturing, and its Future Prospects (Invited), D. Edelstein, IBM TJ Watson Research Center (LINK)

Before the actual copper plating process, the advanced dual-damascene structures for interconnects employ two very important conformal deposition processes :
  • an atomic layer deposition tantalum nitride (ALD TaN) copper diffusion barrier
  • a thin chemical vapor deposition cobalt (CVD Co) liner
More detailed information on Cobalt CVD for barrier/seed and selective encapsulation of copper from the leader Applied Materials can be found here (LINK).

According to a press release below (LINK), Aveni has announced it has obtained results that support the continued use of copper in the BEOL for advanced interconnects, at and beyond the 5nm technology node. Aveni is a French developer and manufacturer of wet deposition technologies and chemistries for 2D interconnects and 3D through silicon via packaging. The company was originally founded in 2001 as a spinoff from the Commissariat à l’énergie atomique et aux énergies alternatives (CEA) to develop and market groundbreaking nanometric deposition technologies for a variety of electronic applications.  

MASSY, France – Dec. 12, 2017 – aveni S.A., developer and manufacturer of market-disrupting wet deposition technologies and chemistries for 2D interconnects and 3D through silicon via packaging, today announced it has obtained results that strongly support the continued use of copper in the back end of line (BEOL) for advanced interconnects, at and beyond the 5nm technology node.

“In this 20th-anniversary year of copper integration, our results validate the comments made by IBM Research Fellow Dan Edelstein in his keynote presentation at the recent IEEE Nanotechnology Symposium, discussing that copper integration is here to stay,” noted Bruno Morel, aveni CEO.

As devices inevitably continue to shrink to meet (and create) market demand, designers are exploring alternative integration schemes, not only for the front end of line, but also the BEOL. This includes, most notably, replacing the copper in dual-damascene interconnects, to compensate for the increased resistance-capacitance (RC) delay that accompanies the thinner copper wires and adversely affects device speed. Proposed replacement options for copper are cobalt, the most likely candidate, or more exotic materials like ruthenium, graphene or carbon nanotubes.

Advanced dual-damascene structures employ an atomic layer deposition tantalum nitride (TaN) copper diffusion barrier, a thin chemical vapor deposition (CVD) cobalt liner, and the electroplated copper fill layer, which makes up most of the wiring. Earlier generations (≥7nm node) also use a physical vapor deposition (PVD) copper seed layer between the cobalt and copper fill, but advanced devices are phasing out this film due to marginal seed coverage and integration hurdles.

Of particular interest is the thin TaN barrier, which prevents copper from diffusing into and poisoning the device. The integrity of the thin cobalt liner (on top of TaN) is critical to ensuring that the barrier functions properly. The reduced thickness of cobalt liners for the 5nm technology node is approaching 3nm, reducing process flexibility for conventional approaches to copper plating.

In a recent study, aveni compared its Sao™ alkaline-based copper electroplating chemistry performance with a conventional, commercially available acidic copper plating chemistry. The samples to be plated were 3nm CVD cobalt over TaN. The study results showed that the acidic copper chemistry attacked the cobalt liner, causing the plating chemistry to react with the underlying TaN film and form tantalum oxide (TaOx). TaOx formation is another failure mode of devices, because it creates an effective open circuit that prevents current flow.

With aveni’s Sao chemistry, the cobalt remained intact and TaOx was not formed, which enables the extension of copper interconnects to process nodes at 5nm and below.

Frédéric Raynal, chief technical officer at aveni, commented, “We were extremely excited about these results, because they substantiate our position that Sao alkaline-based chemistry for copper electroplating is superior to acidic chemistries, especially with the thinner cobalt liners used in advanced nodes.”

aveni will publish the complete findings in a report in early 2018.

1 comment:

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