Mitsubishi, IBM Move on X-ray plans, Medea to study IPL
01/01/1998
Mitsubishi, IBM move on x-ray plans, MEDEA to study IPL
Work at Mitsubishi Electric Corp. and IBM Corp. indicates continued development of an infrastructure for x-ray lithography, with Mitsubishi emerging as a likely test bed for production use. Meanwhile, a public-private group in Europe is addressing ion-projection lithography.
At a recent meeting sponsored by Suss Advanced Lithography in Burlington, VT, a researcher from Mitsubishi Electric reiterated his company`s plan to use x-ray lithography for shrinks of the 256-Mbit DRAM generation. Mitsubishi is reportedly now planning to build a synchrotron-equipped fab facility in Japan.
Mitsubishi has said that x-ray has several advantages over 193-nm optical lithography, such as greater exposure areas and freedom from depth of focus issues. Mitsubishi`s current roadmap, according to a presentation given by Toyoki Kitayama, technical director for the firm`s advanced technology R&D center, predicts x-ray will be an alternative to 193-nm. The company foresees mix-and-match use of both x-ray and direct-write e-beam down to 50 nm (0.05-?m) resolution.
The summit also included presentations by members from other firms researching x-ray, including IBM Corp.`s Pat Hughes, manager of the Advanced Mask facility in Burlington. In an interview, Hughes said his firm has changed its strategy for introducing x-ray. Until recently, he said, IBM has always tried to position x-ray for the current leading technology, but now "our new strategy is we`re going to jump to 0.13."
In 1997, IBM made a strategic switch in its research to use silicon carbide and tantalum as mask membrane and absorber materials instead of using a silicon membrane and gold absorber. Since then, the company has converted its maskmaking capabilities to accommodate the new materials and demonstrated production of masks for 130 nm, 1-Gbit SRAMs, Hughes said.
In 1998, he said, work will begin on producing 100 nm generation masks at Burlington. "We`ve already demonstrated that we`ve got the toolset to be able to do it."
Separately, work is progressing on another post-193-nm option, ion-projection lithography (IPL), under Europe`s MEDEA project. Participating firms and the governments of Austria, Germany, and The Netherlands are taking equal funding positions.
Collaborating in the $36 million, four-year IPL project, which began in April, are Siemens, ASM Lithography, Leica, IMS-Stuttgart, and IMS-Vienna. According to Gerhard Gross, director of Siemens` semiconductor division, IMS-Vienna is building a process development tool to be ready by the second half of 1999. Leica will provide the x-y stage; ASM Lithography will provide an alignment system. The tool will be installed at IMS-Stuttgart in the 1999-2000 time frame. In parallel, Gross said, Siemens will develop stencil masks at its mask house, with the first being produced by the end of this year. "By the beginning of 1999, "we will know how to do the masks," he said. By mid-2000, Gross said Siemens will be able to produce defect-free masks and by 2001 will be in volume production.
Gross said the Medea project will also begin exploring e-beam lithography in the beginning of 1998 and EUV by mid-1998; it will monitor progress of x-ray and projection e-beam (SCALPEL) in the US, because more than one option may be suitable, depending on the application. "We are actually interested in the best technology," he said. The group chose to pursue IPL first because "the time-frame for IPL is that it could be used right after optical," and because it used a 4? stencil mask technology that may be adaptable to SCALPEL and EUV. "With this mask, then we could more or less run the other alternatives. The mask is the big critical factor." - Christine Lunday, WaferNews