Gigaphoton hits 20W with EUV source

19 Feb 2013

Japanese firm is competing with US-based Cymer and others to advance EUV lithography into production.

Lithography light source provider Gigaphoton says that it has now built an extreme ultraviolet (EUV) source with a 20 W peak output and advantages over arch rival Cymer.

The Japanese company, which is competing with US-based Cymer to develop the most advanced light sources for the emerging commercial application of EUV lithography, is set to detail the latest progress in a presentation at the SPIE Advanced Lithography conference being held in San Jose, California, next week.

Both firms are developing laser-produced plasma (LPP) sources, in which a high-power laser is fired at droplets of tin to generate the EUV photons. Gigaphoton’s approach features both a 100 kHz high-power carbon dioxide laser and a separate “pre-pulse” from a solid-state laser to improve the efficiency of EUV light generation. It says that the source can now deliver an average output of 10 W.

The result compares well with the power levels of pre-commercial EUV scanners already in the field, although ASML – currently in the process of acquiring Cymer – said last month that it had now demonstrated a stable 40 W EUV source.

However, for the commercial EUV production runs that are slated to begin in mid-2014, a stable power of 105 W is required. That would be sufficient to support production of 70 wafers per hour, but ramping the EUV source power to such levels while retaining good stability has proved to be an enormous technical challenge and has been beset by delays. Gigaphoton had been scheduled to deliver a 50 W source to ASML last year, for example.

Debris mitigation and pre-pulse key
Gigaphoton believes that its laser pre-pulse and debris mitigation approach will give it crucial advantages in terms of EUV conversion efficiencies and source lifetimes, and says it is committed to continuing development efforts targeting an eventual 250 W output.

The company adds that it has introduced several unique EUV technologies over the past decade. They include the development of an “on-demand” tin droplet generator with droplets measuring less than 20 µm, the combination of two lasers to increase EUV conversion efficiency, and the use of a magnetic field for debris mitigation.

To maximize the lifetime of the collector mirror, the Gigaphoton source uses a superconducting magnet to guide any unwanted debris produced when the high-power laser hits the tin droplets towards a so-called “tin catcher”.

Reaching the 10 W milestone brings it one step closer to the performance required for mass production, with Gigaphoton claiming that its approach will extend the lifetime of tin droplet generators inside the EUV tools, as well as reduce downtime and cost.

"The fact that our unique LPP light source technology is now able to achieve the level of EUV output matching that of today's pre-production performance, proves that our vision for high output, low running cost, stable LPP light sources are indeed achievable," said Gigaphoton CEO Hitoshi Tomaru.

"Our efforts will help to bring the industry closer to realizing mass production level EUV lithography scanners.”

• SPIE’s Advanced Lithography conference takes place 24-28 February at the San Jose Convention Center in California, with the latest developments and ongoing challenges in EUV technology forming a key part of the technical program.