Behind the buzz and beyond the hype:
Our Nanowerk-exclusive feature articles
Posted: Mar 09, 2018
Nanopatterning below 5 nm - towards the design of molecular building blocks
(Nanowerk Spotlight) Photolithography, the standard workhorse employed in today's semiconductor industry, has been the driver behind the ability to print increasingly smaller features at a lower cost. In order to facilitate the production of even smaller features, extreme-UV (EUV) lithography, utilizing radiation of wavelength 13.5 nm, is currently being pursued on a global scale, even though it is tremendously complex and expensive (read more: "The long and tortuous path of EUV lithography to full production").
Given the vast, and still rising, cost of optical lithography tools, researchers have considered alternative patterning technologies such as electron beam lithography (EBL), and nanoimprint technology (NIL) in order to enable the manufacturing of next-generation integrated circuits, flash memory, and hard disk drives.
Now that the length scales attainable by top-down lithography are approaching that of bottom-up self-assembly found in polymers and small molecules, scientists are increasingly looking at bottom-up patterning technologies based on self-assembly.
The utilization of organic building blocks as self-assembled etch masks is particularly attractive since the lithographic information is contained in the self-assembling material itself, rather than provided in an exposure step.
Schematic representation of directed self-assembly of liquid-crystalline small molecules, involving a) tailored interfacial interactions, b) topologically structured interfaces, and c) external fields. (Reprinted with permission by Wiley-VCH Verlag)
– Directed self-assembly of organic small molecules
and these fabrication methods:
– Selective infiltration of inorganics in nanoporous materials
– Hybrid organic/inorganic building blocks.
The authors note that with respect to feature sizes, the sub-5 nm features reported in their article are far ahead of the scaling curve pursued by the semiconductor industry. "This observation implies that several critical challenges must be overcome for these materials to be integrated into existing patterning technologies. Most notably, the critical challenges are related to the development of suitable pattern transfer techniques, mechanical stability of the ultrafine features, the application of appropriate metrology tools, and the integration of the required processing operations into fabrication facilities."
They go on to discuss the challenges and bottlenecks that are facing the industry: integration; pattern transfer; defect density and alignment; and metrology.
"Recent advances in precise morphological control present unique opportunities for obtaining highly ordered, hybrid organic/inorganic sub-5 nm nanostructured morphologies," the authors conclude. "Coupled with directed self-assembly for 3D orientational control and large-area alignment, this exciting class of materials could lead to a broad range of impending nanotechnologies, most notably nanopatterning. Given the impact of these technologies, it is foreseeable that this thrilling field will continue to expand at a rapid pace."