Elongation of extreme ultraviolet (at 13.5 nm) emission with time-of-flight controlled discharges and lateral fuel injection

Abstract

A way toward a quasicontinuous extreme ultraviolet ͑EUV͒ radiation source is proposed and explored. Tin and lithium vapor discharges with the lateral laser-ablation injection are experimentally studied as possible efficient sources of quasicontinuous emission of EUV radiation at a wavelength of 13.5 nm. It is shown that the time-of-flight control of optimal plasma parameters by means of varying ablating laser pulse parameters provides a considerable elongation of maximal-power EUV emission with an overall efficiency of 0.1% and with an energy output exceeding 1% of the energy deposited in the discharge plasma. Along with a high average power and a stable position, such an emitter may have its size small enough to be used in the projection lithography.

High brightness extreme ultraviolet (at 13.5 nm) emission from time-of-flight controlled discharges with coaxial fuel injection

“…9. A pair of electrodes is set at the center axis inside the vacuum chamber, where the source plasma for the EUV emission is produced.…”

“…9 One of the serious problems in the way of creating a practical EUV source in conventional discharge schemes is the short plasma lifetime. 1 Laser produced plasma ͑LPP͒ and discharge produced plasma ͑DPP͒ have been extensively studied as possible efficient sources of 13.5 nm wavelength incoherent radiation 2-6 with the required characteristics for projection lithography: 7,8 a high average power and a small size of emitters.…”

“…1 Laser produced plasma ͑LPP͒ and discharge produced plasma ͑DPP͒ have been extensively studied as possible efficient sources of 13.5 nm wavelength incoherent radiation 2-6 with the required characteristics for projection lithography: 7,8 a high average power and a small size of emitters. 9 The plasma jets are shown to be most efficient when it is produced by the laser ablation. 9 One of the serious problems in the way of creating a practical EUV source in conventional discharge schemes is the short plasma lifetime.…”

“…Recently, time-of-flight controlled discharges with tin and lithium vapor have been shown to be good candidates for practical source of EUV radiation. 9, the fuel injection was made laterally; that means the vapor jet crossed the discharge axis at 90°angle. Even though the high conversion efficiency, about 5%, has been achieved in both LPP and DPP plasmas, the extracted average energy remains quite small because of a short radiation time.…”

Counter-facing plasma focus system as a repetitive and/or long-pulse high energy density plasma source

“…Because a discharge can last for tens of microseconds, then the lifetime of the EUV plasma can be extended, 11,12 which should significantly increase the plasma efficiency and greatly expand the electrode lifetime.…”