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TSMC details litho roadmap, taps maskless

Posted: 03 Mar 2009 ?? ?Print Version ?Bookmark and Share

Keywords:next gen lithography? TSMC litho roadmap? maskless technology?

Taiwan Semiconductor Manufacturing Co. Ltd has disclosed its lithography roadmap and said it is still backing maskless technology at the SPIE Advanced Lithography conference.

The silicon foundry giant TSMC is ramping up its 40nm logic process, with plans to ship its new and previously-announced 28nm technology in 2010. Both the 40- and 28nm processes will use 193nm immersion lithography, said Burn Lin, senior director of the micropatterning division at TSMC.

The real question at TSMC is the 22nm node and beyond. For 22nm, the company is evaluating double-patterning, EUV and maskless. IBM Corp. and others are pushing computational lithography for 22nm, but Lin calls that scheme a resolution enhancement technique (RET)!and not a next-generation lithography (NGL) technology.

Considered the innovator behind immersion, Lin said that 193nm "wet" technology can be extended to the 15nm node (22nm half-pitch logic), thanks in part to double patterning.

NGL dilemma
Like many chipmakers, TSMC may have to resort to double patterning; the so-called NGL technologies are not ready. The trouble with double patterning is that it is "too expensive," Lin said.

If the other NGLs are late!and there is no choice in the matter!Lin said he preferred a double-patterning scheme called litho-litho-etch (LLE), "because of cost."

In doubling patterning, an IC maker is essentially doubling the process steps, thereby boosting production costs. LLE may be cheaper than the rival litho-etch-litho-etch (LELE) method, but LLE uses newfangled processes that are somewhat unproven. LLE uses two lithography exposures and two resist layers to create smaller IC features. In comparison, LELE uses two lithography exposures and hard-mask etches to create smaller features.

A third method is called spacer or self-aligned double patterning. "Spacer is a double patterning technique that uses deposition, anisotropic (directional) etching and trimming to produce smaller features on chips," according to ASML Holding NV.

Beyond doubling-patterning, there are a range of choices. Some are pushing extreme ultraviolet (EUV), which uses 13.5nm wavelength technology. As reported, EUV lithography has been dogged by delays due to the lack of sources, resists and masks. EUV is now being targeted for the 16nm node.

EUV is 'too expensive," he said. The prices for EUV "are difficult to pin down."

TSMC has yet to order an EUV tool. The company's main tool supplier!ASML Holding NV!is currently selling a "pre-production" EUV tool, which will ship next year. EUV tool costs are estimated to be about $90 million.

Like EUV, Lin is not a big fan of nanoimprint lithography. There are some defect concerns about 1x masks and the template process in IC production, he said.

As in previous years, Lin said his "preferred" NGL is maskless technology, which eliminates the photomask in the IC flow. At 22nm, TSMC would like to put maskless in mass production!in all of its fabs. The foundry giant itself has invested in Mapper Lithography NV, a developer of maskless tools.

Mapper is slated to deliver a "pre-alpha" tool to TSMC by the 2H 09, Lin said, adding that he is also watching the other maskless players, such as IMS, KLA-Tencor, TEL/Multibeam and others.

The goal for maskless is to have a machine that sells for $5 million euros ($6.3 million) and produces 10 wafers an hour, he said.

Maskless is a lower-cost technology, but it has been under-funded and is not mature. It's unclear if maskless will pan out, as the clock is ticking on the technology. Vendors have been working on maskless for years. 2009 or 2010 "will be very critical for multi-beam e-beam" technology, he added.

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