Gigaphoton Affirms Debris Mitigating Technology of LPP Light Sources for EUV Lithography

Gigaphoton declared that the company is planning to ship its innovative technology for debris mitigation using magnetic fields in 2012 for laser-produced plasma (LPP) type light sources.

This announcement is a confirmation of the fact that the company’s debris mitigation technology with magnetic fields can eliminate 92% of debris. The debris mitigation technology has been tested many times. The company has taken an important step towards shipping a large-scale production model in the start of 2012.

The validated debris mitigation technology using magnetic fields enables lowering of the amount of Sn (tin) collected on the collector mirror and also reduces damage to the mirror’s multi-layer film. The company expects that this technology will be critical for complete production models of LPP light sources used in EUV lithography.

The proposed technology combines optimally the pre-pulse resulting from a solid-state laser with the main pulse resulting from a CO₂ laser to restrict the creation of neutral Sn atoms and Sn fragments and allows the ionization of majority of the Sn in a single droplet.

During the experiment, the pre-pulse by a solid-state laser is followed by the main pulse generated from the CO₂ laser to radiate droplets of 20 µm diameter for complete removal of Sn fragments. It has been proved that 93% of droplets get ionized, and with the application of the magnetic power more than 99% of Sn ions are directed to the Sn catcher. As a result, damage to the multi-layer film on the surface of the collector mirror is reduced significantly, which allows the mirror to be reused. Upon radiating with lasers, 7% of the non-ionized Sn atoms get deposited on the collector mirror. The company utilizes etching gas to enable periodical cleaning to eliminate the remaining Sn atoms.

As double-pattern lithography with the help of 193 nm immersion lithography equipment reaches maximum resolution, a short wavelength EUV light source serves as an advanced lithography solution. Stable functioning of the light source has been the key issue in implementation of the EUV lithography tool.