Imec sets major step towards
20nm half pitch interconnects with the realization of electrically functional
copper lines embedded into silicon oxide using a spacer-defined double patterning
Cross sectional TEM analysis of 20nm ½ pitch interconnects after integration into single damascene using a spacer defined double patterning approach.
“We are very proud to be the world’s first in developing and processing
such small on-pitch working interconnects;” said Zsolt Tokei, program
director interconnects at imec. “Spacer-defined (or self-aligned) double
patterning has recently gained interest as the patterning technique for future
FLASH memory devices. I’m confident that memory companies will benefit
from this state-of-the-art result.”
Scaling of interconnects towards 20nm half pitch faces many challenges. Double
patterning lithography is needed since the metal lines cannot be realized in
a single print. Therefore, a solution is needed for the actual design split
of the structures and the alignment of the different masks. And, filling of
(sub-)20nm lines is not possible using standard physical vapor deposition of
TaN/Ta-based metallization. Moreover, control of line-edge roughness becomes
increasingly difficult with further scaling. And finally, engineering of the
patterning stack is required for optimal adhesion.
Imec demonstrated patterning and metallization of 20nm half pitch copper lines
in silicon oxide with a TiN metal hard mask. The patterning is based on a sacrificial
double hard mask and uses 3 photos (CORE, TRIM and PATCH) and four etch steps.
The CORE photo defines dense lines at 40nm half pitch, which after trim, etch
and spacer deposition results in 20nm half pitch spacer loops. The TRIM makes
large openings to cut the spacer loops away by etch. And PATCH defines the final
layout, electrical connections and bond pads. Overlay control is critical in
order to end up with the designed test pattern. The dielectric spacing between
the metal lines was accurately controlled thanks to the spacer-defined integration
method. A Ruthenium-based metallization scheme was used to realize void-less
Dielectric breakdown properties of the interconnects were measured and the
results are very encouraging as the breakdown field is close to the intrinsic
dielectric breakdown properties of the oxide and dielectric cap layers.
These results were obtained in cooperation with imec’s key partners in
its core CMOS programs: Intel, Micron, Panasonic, Samsung, TSMC, Sony, Fujitsu,
Infineon, Qualcomm, ST Microelectronic, Amkor.
Imec performs world-leading research in nanoelectronics. Imec leverages its
scientific knowledge with the innovative power of its global partnerships in
ICT, healthcare and energy. Imec delivers industry-relevant technology solutions.
In a unique high-tech environment, its international top talent is committed
to providing the building blocks for a better life in a sustainable society.
Imec is headquartered in Leuven, Belgium, and has offices in Belgium, the Netherlands,
Taiwan, US, China and Japan. Its staff of more than 1,750 people includes over
550 industrial residents and guest researchers. In 2009, imec's revenue (P&L)
was 275 million euro.
Imec is a registered trademark for the activities of IMEC International (a
legal entity set up under Belgian law as a "stichting van openbaar nut”),
imec Belgium (IMEC vzw supported by the Flemish Government), imec the Netherlands
(Stichting IMEC Nederland, part of Holst Centre which is supported by the Dutch
Government), imec Taiwan (IMEC Taiwan Co.) and imec China (IMEC Microelectronics
(Shangai) Co. Ltd.).