DRAMeXchange Analyzes 50nm Challenge for DRAM Industry

Jul 11, 2008 16:35 Nikkei Electronics Asia

In the DRAM industry, traditional ArF dry lithography equipment is still the mainstream fabrication tool, with its physical limit being identified at 65nm. This implies that for any design geometry that is smaller than 65nm, a shift to immersion tools is necessary.

Immersion tools utilize water to replace air as the media in between the lithography lens and the wafer surface for circuitry patterning. Since water delivers a higher refraction rate, smaller linewidth results, thus breaking the physical limit. According to DRAMeXchange, the vast capex required for process node advancement, especially procurement of expensive immersion tools, is a big challenge for those DRAM makers who are still bleeding in the red.

Process node shrinking is the most efficient way to lower manufacturing cost. Most DRAM technology leaders had their mainstream technology migrated to 70nm. As traditional ArF dry tools have their physical limit beyond 65nm, they have no alternative but to opt for expensive an immersion tool if they wish to keep their foothold in the market. When it comes to cost issues, it will be those with deep pockets that take the leap first.

ASML, Canon and Nikon are the three major immersion tool suppliers. The no.1 vendor ASML has shipped over 70 sets of immersion tools so far, mainly for logic IC makers. Key immersion tools from ASML include Twinscan XT1700i and XT1900Gi. Of these, the XT1900Gi can support process nodes down to <40nm, and there have been shipments to more than 10 customers since 3Q 2007. Nikon started supplying its NSR-S609B for 55nm and 45nm process nodes from 2006. It started shipping the NSR-S610C for 45nm process from 2007.

Besides advancing process nodes, DRAM technology breakthroughs could be achieved through the introduction of copper process. In contrast to the present aluminum process, the copper process is 40% faster, 30% lower in cost and 30% thinner in linewidth. Micron was the first DRAM maker to develop a copper process for DRAM production, with fellow technology leaders also striving to advance their production in this field.

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