Study of a cavity-confined plasma as a debris-less and high conversion efficiency source for EUV lithography

We are proposing a cavity-confined type laser-produced plasma as a debris-less and high conversion efficiency source for EUV lithography. Our idea is devised in order to make the best use of solid target having higher conversion efficiency and easier wavelength tunability than gas targets. In order to overcome the debris problem, two contrivances are made, i.e., ablation of the solid surface by the irradiation of an ultrashort pulse, and enhancement of the ablated mass density by the cavity structure of the target. Preliminary experimental evaluation of the cavity confinement effect and high efficiency EUV emission are reported.