Double-patterning may bail out industry Mark LaPedus (02/23/2006 9:21 H EST) URL: http://www.eetimes.com/showArticle.jhtml?articleID=180207176 SAN JOSE, Calif. — Immersion lithography could be late to the market, forcing chip makers to consider 193-nm “dry” and double-exposure techniques for chip production at the 45-nm node and beyond, according to South Korean memory giants Hynix Semiconductor Inc. and Samsung Electronics Co. Ltd. Many chip makers are scrambling to get 193-nm immersion lithography in production for the 45-nm node in the 2007 time frame. But in separate papers at the SPIE Microlithography conference here this week, Hynix and Samsung indicated that 193-nm immersion is still behind for insertion in the development of NAND-based flash memory devices at the 50-nm node. The lack of immersion lithography will make 193-nm “dry” and double-patterning techniques “unavoidable,” according to a paper from Hynix at SPIE. With 193-nm double-patterning, Hynix claims to have developed a 50-nm, half-pitch NAND device with good CD uniformity. In another paper, Samsung believes that double-exposure is better suited for flash and DRAM manufacturing, as compared to logic production. “Indeed, immersion is not fully ready,” according to a paper from Samsung. “ Double-exposure is becoming a stronger candidate as throughput issues are getting better.” Double-exposure is an expensive technology that has been debated for years. In this technique, to be done with 193-nm “dry” scanners, “each lithography step is completed by a combination of two separate resist and etch steps; hence, the physical limit of resolution, 0.25 k1, can be overcome with in a double-patterning scheme,” according to the Hynix paper. In one presentation, IMEC surprised an audience at SPIE when it noted that 193-nm immersion with double-exposure techniques represents the “lowest risk to the 32-nm half-pitch node.” Extreme ultraviolet (EUV) and 193-nm immersion are also candidates for the 32-nm node, according to IMEC. Double-patterning is an insurance policy for the semiconductor industry — if the other solutions do not work, said Farhad Moghadam, senior vice president and general manager of the Thin Films product business group at Applied Materials Inc. (Santa Clara, Calif.). But besides the costs, there are some overlay issues associated with double-patterning, Moghadam said. At 45-nm, chip makers may end up inserting 193-nm “dry” with double-exposure instead of immersion, which could miss the market window, he said. “Immersion will eventually happen,” he said, but “it’s very unlikely” that chip makers will insert the technology at the 45-nm node. Still, others are moving full speed ahead with immersion despite the current and nagging defect issues with the fledging technology. Silicon foundry giant Taiwan Semiconductor Manufacturing Co. Ltd. (TSMC) said that immersion lithography is “nearly production ready.” TSMC claimed that its immersion lithography program has produced test wafers well within acceptable parameters for volume manufacturing. TSMC's immersion lithography technology is targeted for its 45-nm manufacturing process, which is slated for 2007 or so. Chartered, IBM, Infineon, TI and others are also banking on immersion for 45-nm. And the tool makers themselves claim that they are on track with the systems. After shipping its first hyper NA tool, Japan’s Nikon Corp. disclosed the details of its next-generation immersion lithography tool for use in chip making down to the 32-nm node. Nikon’s new scanner, dubbed the NSR-S610C, is a 193-nm immersion tool with an NA of 1.30. Defects are not an issue with Nikon’s immersion scanners, said Soichi Owa, Nikon Fellow and development manager for Nikon (Tokyo), in a presentation SPIE. The S610C system is geared for memory production down to the 45-nm half-pitch node and logic chip manufacturing at 32-nm, said Bernie Wood, director of marketing at Nikon Precision Inc. (Belmont, Calif.). Shipments are due by year ’s end. Nikon’s rival, ASML Holding NV, will shortly ship its first hyper NA tool, the Twinscan XT:1700i, a machine geared for the 45-nm node. “We’re on track, ” said Peter Jenkins, vice president of marketing for ASML (Veldhoven, the Netherlands). “It’s the only machine in the market that can support 45-nm.” That system is made using a combination of a 1.2 NA catadioptric lens, polarized illumination and water based immersion technology. ASML expects to ship between 20 and 25 Twinscan XT:1700i immersion lithography systems in 2006. And not to be outdone, Canon Inc. is expected to ship a 193-nm immersion tool with an NA of 1.30 by the end of this year or early next year. --

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