Lithography light source manufacturer, Gigaphoton claims that its debris mitigating technology, using magnetic fields for laser-produced plasma (LPP) light sources for EUV lithography is capable of removing 92% of debris, which means the technology will enter mass production, and shipments start in early, 2012.
“It has been confirmed by this achievement with the mass-production LPP light source that our unique LPP light source technologies can be implemented to ensure stable operation at lower running cost,” noted Dr Yuji Watanabe, president of Gigaphoton. “I believe this will further increase momentum for device manufacturers to introduce EUV lithography tools as the next-generation lithography technology. We at Gigaphoton has already started operating the factory dedicated to initial mass-production of the EUV light sources in order to meet our customers’ request for shipment in the beginning of 2012. So, we are on track to prepare for the EUV business.”
According to Gigaphoton, an LPP light source allows radiation of a CO2 laser onto the Sn target (droplets), which are deposited on the collector mirror as well damage the multi-layer film of the mirror. The debris mitigation technology with magnetic fields is claimed by the company to be indispensable for full-production models of LPP light sources for EUV lithography.
The Gigaphoton-proposed debris mitigation uses an optimum combination of the pre-pulse generated by a solid-state laser and the main pulse generated by a CO2 laser to suppress the generation of Sn fragments and neutral Sn atoms and ionize most of the Sn in each droplet. Ionized Sn is guided to the Sn catcher by magnetic energy and then removed to minimize deposition and damage to the collector mirror.
Gigaphoton said that during the verification experiment, the main pulse of the CO2 laser is radiated to each droplet of 20 µm in diameter following the pre-pulse of a solid-state laser to completely eliminate Sn fragments.
The company claims that 93% of droplets are ionized, and then optimum magnetic power applied to these droplets guides more than 99% of Sn ions to the Sn catcher.
According to Gigaphoton, the 7% of non-ionized Sn atoms after laser radiation may slowly deposit on the collector mirror. However, Gigaphoton uses etching gas to allow regular cleaning and thereby remove all of these remaining Sn atoms.
This allows the minimization of damage to the multi-layer film on the collector mirror surface. It also becomes a clue for making the mirror reusable.
The remaining 7% of non-ionized Sn atoms after laser radiation may slowly deposit on the collector mirror. However, Gigaphoton uses etching gas to allow regular cleaning and thereby remove all of these remaining Sn atoms.