EUV Sources for Lithographic Applications

Semiconductor device manufacturing is currently using excimer lasers as the light source for lithographic structuring. The wavelength of these ArF lasers is 193 nm and the high volume manufacturing of structures with 45 nm has started already. To further shrink the structure size to 32 nm and beyond, a reduction of the used wavelength is required for physical reasons. The next technology will be the extreme ultraviolet (EUV) lithography using light with 13.5 nm wavelength. Efficient optical elements like multi layer optics were developed in the last years using improvements in thin film technology on large area substrates with roughness in the sub­nanometer range. Sources for such light are plasma based sources in which the plasmas are generated either by electrical gas discharges or by pulsed laser radiation. In this paper we describe the discharge produced plasma (DPP) sources only because of their advantages concerning efficiency, simplicity, reliability and maturity.