Lithography is at a crossroads, and it could be headed in the wrong direction.
Lithography is the key production technology behind the IC process-scaling cycle articulated by Moore's Law. The current technology has remained viable far longer than anyone expected, but it could run out of steam in the near future. Work on a successor began decades ago.
Today, however, three of the four dominant next-generation lithography (NGL) candidates-extreme ultraviolet (EUV), multibeam maskless and nanoimprint-are behind schedule.
Clockwise from top left, nanoimprint results for: close-packed microlenses, 45-nm-node logic chip patterns, 32-nm-node memory chip contacts, and multitier imprinted insulator with 100-nm-diameter via. Courtesy of Molecular Imprints Inc.
EUV, in particular, has consumed considerable R&D time and treasure but still has little to show for it, prompting calls from some circles for development efforts to be redirected elsewhere. Nanoimprint, for its part, has overlay and throughput problems, and multibeam remains in R&D.
The fourth NGL candidate, directed self-assembly, is a promising research topic that is nowhere near development.
The industry has long known that without a viable NGL solution-which most assumed would be EUV-Moore's Law scaling would "slow" and "the secular growth rate of the semiconductor industry would decline," as Piper Jaffray & Co. analyst Gus Richard put it. Adoption of 193-nm immersion lithography bought the industry some time to get its act together on NGL.
But with timetables slipping on EUV and other next-gen solutions, "the top priority is still to extend" 193 nm, said Hans Pfeiffer, proprietor of HCP Consulting Services. Toward that end, chip makers are pursuing techniques such as double patterning, adding complexity and cost to an already prohibitively expensive undertaking.