Bjoern A. M. Hansson

A liquid-xenon-jet laser-plasma x-ray and EUV source

We describe a laser-plasma soft-x-ray source based on a cryogenic-xenon liquid-jet target. The source is suitable for extreme ultraviolet (EUV) projection lithography and proximity x-ray lithography (PXL). Absolute calibrated spectra in the 1-2 nm range and uncalibrated spectra in the 9-15 nm range are obtained using a free-standing transmission grating and a CCD-detector.

Xenon liquid-jet laser-plasma source for EUV lithography

We describe a laser-plasma source based on a cryogenic xenon liquid-jet target suitable for extreme ultraviolet (EUV) projection lithography. Recent improvements in the stability of the xenon jet allows efficient laser-plasma operation several millimeters away from the nozzle orifice. We present the first preliminary laser-to-EUV conversion efficiencies, although under non-optimized conditions, for the source.

Status of the liquid-xenon-jet laser-plasma source for EUV lithography

The liquid-xenon-jet laser-plasma source is one of the extreme-ultraviolet (EUV) source technologies under development for EUV lithography. This paper presents some recent improvements of the technology, including the ability to operate a stable plasma at a distance of 50 mm from the nozzle, the first positive mirror-lifetime results, and improved laser-to-EUV conversion efficiency of 0.75 percent at lambda equals 13.45 nm.

Stability of droplet-target laser-plasma soft x-ray sources

The spatial stability of microscopic target droplets used for laser-plasma soft x-ray generation in vacuum is investigated. A long-term drift in drop position is characterized with an ultrafast laser-diode imaging system. The drift is experimentally and theoretically shown to be due to a temperature-induced increase in target-liquid viscosity as a result of evaporation. Finally, the drift is compensated for and stable, long-term unattended operation of the source is demonstrated with an automatic phase-delay drop-to-laser synchronizing system. This is important for future compact lithography and microscopy systems.

X-ray and EUV laser-plasma sources based on cryogenic liquid-jet target

We describe new high-brightness laser-plasma sources for x- ray and extreme UV (EUV) radiation. By utilizing a microscopic liquid-jet or liquid-droplet target the harmful emission of debris is significantly reduced or completely eliminated. The spectrum can be spectrally tailored by choosing a suitable liquid. In this paper we summarize our work on this type of source and include some recent developments on cryogenic liquified gases such as nitrogen and xenon. We believe that this new source is a suitable choice for EUV lithography as well as for proximity x-ray lithography.

Liquid-Xenon-Jet Laser-Plasma Source for EUV Lithography

The liquid-xenon-jet laser-plasma source is one of the extreme-ultraviolet (EUV) source technologies under development for EUV lithography. This paper discuss the basic, demanding, requirements of a source for EUV lithography including high in-band EUV power, absence of mirror contamination and high stability. It is further discussed how the liquid-xenon-jet can meet these requirements, and specifically how the ability to operate the plasma far from any mechanical details such as the nozzle will facilitate high power operation with low resulting mirror degradation. Furthermore, a new laser-to-EUV conversion efficiency result of 0.55%/(2%BW 2pisr) at lambda=13.45 nm is presented together with a detailed description of the method for calibrated EUV-power measurement.

Target analysis of laser plasma droplet-target system

In this paper the speed of microscopic droplets used as targets for laser-plasma soft x-ray generation is investigated. The speed is measured for a variety of liquids with different hydrodynamic properties and at different pressures. A theoretical model is then adapted to predict the speed of the jet, given the applied pressure and the physical properties of the liquid. Since certain liquids with low surface tension and cryogenic liquids are interesting for laser-plasma generation, obtaining a model for the speed of the liquid is important, as the speed cannot be easily measured for these liquids.

Liquid-target laser-plasma sources for EUV and x-ray lithography

We review the development of compact laser-plasma soft x-ray sources based on microscopic liquid drops or liquid jets as target. It is shown that such sources provide practically debris-free, high-flux operation at wavelengths suitable for EUV and x-ray lithography. This regenerative and liquid- density target system holds promise for high-average power x- ray and EUV generation using high-repetition-rate lasers. Application of the method to compact x-ray microscopy is also briefly discussed.