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Quest for the right road to lithography

Posted: 07 Apr 2010 ?? ?Print Version ?Bookmark and Share

Keywords:lithography? extreme ultraviolet? EUV? next-generation lithography?

Lithography is at a crossroads and could very well 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.

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 solutionwhich most assumed would be EUVMoore'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 193nm immersion lithography bought the industry some time to get its act together on NGL.

But with timetables slipping on EUV and other NGL solutions, "the top priority is still to extend" 193nm, said Hans Pfeiffer, proprietor of HCP Consulting Services. Toward that end, chipmakers are pursuing techniques such as double patterning, adding complexity and cost to an already prohibitively expensive undertaking.

Clockwise from top left, nanoimprint results for: close-packed microlenses, 45nm logic chip patterns, 32nm memory chip contacts, and multitier imprinted insulator with 100nm-diameter via. Courtesy of Molecular Imprints Inc.

EUV woes
ASML Holding NV and Nikon Corp. have developed immersion scanners that they say offer higher throughput to offset double patterning's cost. But ASML has pushed back the ship date slightly for its scanner, and the two rivals are trading jabs, each claiming the other's new model does not meet advertised specifications.

EUV, for its part, has been a money pit. The industry recently made the embarrassing admission that it still lacks metrology tools for EUV and now requires $200 million or more to develop them. A preproduction EUV tool from ASML costs a staggering $90 million. Meanwhile, adequate power sources for EUV aren't available, defect-free EUV masks haven't been achieved, and the resists for the technology aren't ready.

Intel Corp. in 1997 led the formation of the EUV LLC consortium with a plan to commercialize the technology by 2005 for the 90nm node, but the industry is still waiting for commercially viable EUV tools. Samsung says it believes EUV is doable by 2012, but most industry estimates put the rollout date closer to 2015. Intel now plans to extend immersion lithography down to 11nm, and it is weighing maskless as well as EUV technology for the NGL shift.

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