Ruthenium could play a key role in helping to identify metallisation solutions for 22-nm nodes, it emerged on Tuesday (14th July).

Research consortium IMEC revealed at the Semicon West conference that it has been conducting tests to improve the design and manufacturing potential of the nodes.

Its investigations focused on the formation of copper interconnect lines, allowable geometrics for interconnect and the reliability of the porous low-k dielectric materials.

The lines are generally created by putting copper into grooves in the dielectric material, but the resulting diffusion tends to poison the latter so a thin layer of tantalum separates them.

However, a further problem then arises because tantalum prevents the copper from moving and copper crystals from forming, meaning that a 'seed layer' is required to correct the process.

While this works for 45-nm nodes, there is a major tendency in their 22-nm counterparts for both the barrier and seed layers to affect the top of the groove before any copper has even arrived.

IMEC found that replacing the traditional physical vapour deposition process with a chemical vapour deposition process - using a ruthenium seed - offered a significant improvement.

The group attempted a number of different barrier/seed combinations but concluded that a ruthenium-tantalum approach would be the best for addressing copper at 22nm.

In addition, IMEC explained that similar processes could prove effective in smaller nodes and allow them to be regarded as an invaluable part of technological advances.

"We are confident we will have interconnect solutions for the 20-nm half pitch, and ten-nm structures are currently under investigation," Rudi Cartuyvels, Vice President and General Manager of Technology at IMEC, was quoted as saying by semiconductor.net.

Sources:

Industry takes aim at 22-nm interconnect stack (14/07/09)

IMEC Reveals Interconnect Roadmap to 10 nm (14/07/09)

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