Mask write times are getting uncomfortably long, and a potential solution is to employ the multi-electron-beam approach for mask writers. Sematech CEO Dan Armbrust, in a keynote speech at the 2010 Sematech Litho Forum going on this week in New York City, said the consortium may form a multi-beam mask writer program late this year.
At least six companies are developing multi-beam direct-write systems for maskless wafer patterning. One or more of those companies may attempt to direct their multi-beam capabilities to the mask writing space, with Vistec Electron Beam GmbH (Jena, Germany) expressing interest in joining the proposed multi-beam mask writer (MBMW) consortium. The two leading mask writer vendors, JEOL and Nuflare, both based in Japan, also may join the planned Sematech program, said a senior Sematech manager based in Albany, N.Y.
Other multi-beam direct write companies, such as Mapper Lithography NV (Delft, Netherlands) and IMS Nanofabrication AG (Vienna, Austria) have indicated that they will continue to focus on the opportunities in maskless lithography, or ML2, the Sematech manager said.
KLA-Tencor (Milpitas, Calif.), another company developing an ML2 solution, would be willing to license its technology to a mask writer vendor but also does not intend to divert its own resources to the multi-beam mask writer field, he said.
Chris Progler, CTO at mask manufacturer Photronics, Inc. (Brookfield, Conn.), said mask write times could be speeded up by employing a relatively modest number of beams, up to about 256 beams. That is far fewer than the 13,000 beams envisioned by Mapper for its production-level wafer patterning machine. “This is one of most interesting things to come along in the last year for the mask industry,” Progler said.
Currently, most e-beam based mask writers use variable-shaped beam (VSB) technology in a single-beam configuration, while laser-based writers from Applied Materials Inc. (Santa Clara), for example, already successfully employ a multi-beam approach.
During a Monday workshop on multi-beam technology preceding the two-day Litho Forum, Franklin Kalk, CTO of Toppan Photomasks Inc., said the 32-beam Alta laser mask writer from Applied Materials performs well, with relatively little downtimes. “That laser approach could be extended to e-beam writers, giving the industry as 2-10x reduction in write times,” Kalk said.
Toppan estimates that mask write times average 8.5 hours, though 5% of all masks take more than 16 hours to write. “We are now seeing a dramatic increase in write times at the 32 nm generation – two to three times longer than at the 65 nm node, even though the tools have improved,” Kalk said.