Abstract: The present invention provides methods and apparatus for facilitating the start up of a fuel droplet stream generator. During a start-up phase the fuel droplet stream generator is positioned so that the fuel droplets re emitted downwardly whereby gravity assists in the establishment of the stream. The droplets are monitored using a visualization system and once the stream is determined to have the desired characteristics the stream generator is moved to a second position of steady state use in which the droplet stream is emitted in a horizontal direction.

Abstract: The present invention provides a method of monitoring the operation of a radiation source fuel droplet stream generator comprising a fuel-containing capillary and a piezo-electric actuator (500). The method comprises analysing the resonance frequency spectrum of a system comprising the fuel-containing capillary and the piezo-electric actuator in particular to look for changes in the resonance frequencies of the acoustic system which may be indicative of a change in the properties of the system requiring investigation.

Abstract: A radiation source for generating EUV from a stream of molten metal fuel droplets by LPP (Laser Produced Plasma) or (Dual Laser Plasma) has a fuel droplet generator arranged to provide a stream of droplets of fuel and at least one laser configured to vaporise at least some of said droplets of fuel, whereby radiation is generated. The fuel droplet generator has nozzle, fuel supply line, and reservoir, with a pumping device arranged to supply a flow of molten metal fuel from the reservoir through the fuel feed line and out of the nozzle as a stream of droplets. The fuel droplet generator has a replaceable filter assembly in the fuel feed line, arranged to filter the molten metal fuel in use, to deter nozzle blockage by solid particulate impurities in the fuel.

Abstract: A radiation source for generating EUV from a stream of molten metal fuel droplets by LPP (Laser Produced Plasma) or (Dual Laser Plasma) has a fuel droplet generator arranged to provide a stream of droplets of fuel and at least one laser configured to vaporise at least some of said droplets of fuel, whereby radiation is generated. The fuel droplet generator has nozzle, fuel supply line, and reservoir, with a pumping device arranged to supply a flow of molten metal fuel from the reservoir through the fuel feed line and out of the nozzle as a stream of droplets. The fuel droplet generator has a replaceable filter assembly in the fuel feed line, arranged to filter the molten metal fuel in use, to deter nozzle blockage by solid particulate impurities in the fuel.

Abstract: A radiation source having a nozzle configured to direct a stream of fuel droplets along a trajectory towards a plasma formation location, a laser configured to direct laser radiation at the fuel droplets at the plasma formation location to generate, in use, a radiation generating plasma. The nozzle has an internal surface that is configured to prevent contamination present in fuel used to form the fuel droplets from being deposited on that internal surface.

Abstract: A radiation source includes a nozzle configured to direct a stream of fuel droplets along a trajectory towards a plasma formation location; a laser configured to output laser radiation, the laser radiation directed at the fuel droplets at the plasma formation location to generate, in use, a radiation generating plasma; and a catch configured to catch fuel droplets that pass the plasma formation location. The catch includes a container configured to contain a fluid; a driver configured to drive the fluid, to cause the fluid to move; the catch being configured such that the fuel droplets are incident on that moving fluid.

Abstract: A lithographic apparatus includes a source configured to generate a radiation beam comprising desired radiation and undesired radiation using a plasma, an illumination system configured to condition the radiation beam and to receive hydrogen gas during operation of the lithographic apparatus, and a support structure constructed to hold a patterning device. The patterning device is capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam. A substrate table is constructed to hold a substrate, and a projection system is configured to project the patterned radiation beam onto a target portion of the substrate. The lithographic apparatus is configured such that the radiation beam on entering the projection system includes at least 50% of the undesired radiation that is generated by the plasma and includes wavelengths of radiation that interact with the hydrogen gas to generate hydrogen radicals.

Abstract: A lithographic apparatus includes a magnet being contained in a protective enclosure, the protective enclosure being arranged to protect the magnet from contact with a H2-containing or H-atom containing gas. The enclosure may further contain a hydrogen getter, such as a magnet-surface modifying gas, or a non-hydrogen containing gas. A non-hydrogen containing gas flow may be provided or a non-hydrogen getter gas flow may be provided through at least part of the protective enclosure.

Abstract: A collector mirror assembly includes a collector mirror that includes a reflective surface and a hole having an edge. The hole extends through the reflective surface. The assembly also includes a tubular body having an inner surface and an outer surface. The tubular body is constructed and arranged to guide a gas flow in a direction substantially transverse to the reflective surface. The outer surface of the tubular body and the edge of the hole form an opening arranged to guide a further gas flow that diverges with respect the gas flow substantially transverse to the reflective surface.

Abstract: According to a first aspect of the present invention, there is provided a radiation source comprising: a reservoir configured to retain a volume of fuel; a nozzle, in fluid connection with the reservoir, and configured to direct a stream of fuel along a trajectory towards a plasma formation location; a laser configured to direct laser radiation at the stream at the plasma formation location to generate, in use, a radiation generating plasma; and a contamination filter assembly located in a fuel flow path of the radiation source, upstream of a nozzle outlet, a filter medium of that contamination filter assembly being held in place within the contamination filter assembly by a clamping force provided by one or more objects that at least partially surround the filter medium.

Abstract: There is provided a multilayer mirror (80) comprising a layer of a first material (84) and a layer of silicon (82). The layer of the first material and the layer of silicon form a stack of layers. An exposed region of the layer of silicon comprises a modification that is arranged to improve the robustness of the exposed region of silicon.

Abstract: A radiation source generates extreme ultraviolet radiation for a lithographic apparatus as a chamber that is provided with a low pressure hydrogen environment. A trace amount of a protective compound, e.g., H2O, H2O2, O2, NH3 or NOx, is provided to the chamber to assist in maintaining a protective oxide film on metal, e.g., titanium, components in the chamber.

Abstract: A method of reducing contamination generated by a hydrogen radical generator and deposited on an optical element of a lithographic apparatus includes passing molecular hydrogen over a first part of a metal filament of the hydrogen radical generator, the first part including a metal-oxide, when the temperature of the first part of the metal filament is at a reduction temperature less than or equal to an evaporation temperature of the metal-oxide.

Abstract: A lithographic apparatus includes a source configured to generate a radiation beam comprising desired radiation and undesired radiation using a plasma, an illumination system configured to condition the radiation beam and to receive hydrogen gas during operation of the lithographic apparatus, and a support structure constructed to hold a patterning device. The patterning device is capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam. A substrate table is constructed to hold a substrate, and a projection system is configured to project the patterned radiation beam onto a target portion of the substrate. The lithographic apparatus is configured such that the radiation beam on entering the projection system includes at least 50% of the undesired radiation that is generated by the plasma and includes wavelengths of radiation that interact with the hydrogen gas to generate hydrogen radicals.

Abstract: A lithographic apparatus includes a magnet being contained in a protective enclosure, the protective enclosure being arranged to protect the magnet from contact with a H2-containing or H-atom containing gas. The enclosure may further contain a hydrogen getter, such as a magnet-surface modifying gas, or a non-hydrogen containing gas. A non-hydrogen containing gas flow may be provided or a non-hydrogen getter gas flow may be provided through at least part of the protective enclosure.

Abstract: An amount of oxides in an apparatus having a chamber containing an amount of contamination material and an amount of the oxides, the oxides being oxides of the contamination material, is reduced. In the method, a hydrogen containing gas is provided in at least part of the chamber. A predetermined minimum partial hydrogen gas pressure and a predetermined maximum partial oxidants pressure is established in the chamber. In the chamber, a temperature is maintained which is at least higher than a temperature at which, in thermodynamic equilibrium given the predetermined maximum partial oxidants and minimum partial hydrogen gas pressures as established, the amount of contamination material is at least 10 times higher than the amount of oxides.

Abstract: The invention provides a cleaning process for the removal of deposition on an element of a lithographic apparatus. The method includes (ex situ) treating the element with an alkaline cleaning liquid. In this way, Sn may be removed from a contaminant barrier or a collector mirror. Especially beneficial is the application of a voltages to the element to be cleaned and/or by using complexing agents for improving the dissolution of Sn in the cleaning liquid.