Abstract: A method of forming a spectral purity filter having a plurality of apertures configured to transmit extreme ultraviolet radiation and suppress transmission of a second type of radiation, in which trenches are formed in a base material in a pattern corresponding to the walls to be formed between the apertures. The trenches are filled with a grid material to form walls of the grid material, and the base material is selectively removed until the grid material is exposed and forms the spaces between the walls of the grid material for the apertures.

Abstract: A radiation source includes an uncapped Mo/Si multilayer mirror, and a cleaning apparatus configured to remove a deposition comprising Sn on the uncapped Mo/Si multilayer mirror. The cleaning apparatus is configured to provide a gas comprising one or more of H2, D2 and HD and one or more additional compounds selected from hydrocarbon compounds and/or silane compounds in at least part of the radiation source, to produce hydrogen and/or deuterium radicals and radicals of the one or more additional compounds, from the gas, and to supply the hydrogen and/or deuterium radicals and radicals of the one or more additional compounds to the uncapped Mo/Si multilayer mirror to remove at least part of the deposition.

Abstract: A spectral purity filter is configured to reflect extreme ultraviolet radiation. The spectral purity filter includes a substrate, and an anti-reflective coating on a top surface of the substrate. The anti-reflective coating is configured to transmit infrared radiation. The filter also includes a multi-layer stack configured to reflect extreme ultraviolet radiation and to substantially transmit infrared radiation.

Abstract: A lithographic apparatus includes a plasma source that includes a vessel configured to enclose a plasma formation site, an optical device configured to transfer optical radiation to or from the vessel, and a reflector arranged in an optical path between the optical device and the plasma formation site source. The reflector is configured to reflect the optical radiation between the optical device and the plasma formation site. The reflector is formed, in operation, as a molten metal mirror.

Abstract: A radiation source includes an uncapped Mo/Si multilayer mirror, and a cleaning apparatus configured to remove a deposition comprising Sn on the uncapped Mo/Si multilayer mirror. The cleaning apparatus is configured to provide a gas comprising one or more of H2, D2 and HD and one or more additional compounds selected from hydrocarbon compounds and/or silane compounds in at least part of the radiation source, to produce hydrogen and/or deuterium radicals and radicals of the one or more additional compounds, from the gas, and to supply the hydrogen and/or deuterium radicals and radicals of the one or more additional compounds to the uncapped Mo/Si multilayer mirror to remove at least part of the deposition.

Abstract: A metal component (262M, 300M) is designed for use in an EUV lithography apparatus, for example as a spectral purity filter (260) or a heating element (300) in a hydrogen radical generator. An exposed surface of the metal is treated (262P, 300P) to inhibit the formation of an oxide of said metal in an air environment prior to operation. This prevents contamination of optical components by subsequent evaporation of the oxide during operation of the component at elevated temperatures.

Abstract: A radiation source is configured to generate radiation. The radiation source includes a first electrode and a second electrode configured to produce an electrical discharge during use to generate radiation-emitting plasma from a plasma fuel. The radiation source also includes a fuel supply configured to supply a plasma fuel to a fuel release area that is associated with the first electrode and the second electrode, and a fuel release configured to induce release of fuel, supplied by the fuel supply, from the fuel release area. The fuel release area is spaced-apart from the first electrode and from the second electrode.

Abstract: A method for removal of a deposition on an uncapped multilayer mirror of an apparatus. The method includes providing a gas that includes one or more of H2, D2, and DH, and one or more additional compounds selected from hydrocarbon compounds and/or silane compounds in at least part of the apparatus; producing hydrogen and/or deuterium radicals and radicals of the one or more additional compounds, from the gas; and bringing the uncapped multilayer mirror with deposition into contact with at least part of the hydrogen and/or deuterium radicals and the radicals of the one or more additional compounds to remove at least part of the deposition.

Abstract: According to an aspect of the present invention, a spectral purity filter includes an aperture, the aperture being arranged to diffract a first wavelength of radiation and to allow at least a portion of a second wavelength of radiation to be transmitted through the aperture, the second wavelength of radiation being shorter than the first wavelength of radiation, wherein the aperture has a diameter greater than 20 ?m.

Abstract: A spectral purity filter includes a body of material, through which a plurality of apertures extend. The apertures are arranged to suppress radiation having a first wavelength and to allow at least a portion of radiation having a second wavelength to be transmitted through the apertures. The second wavelength of radiation is shorter than the first wavelength of radiation. The body of material is formed from a material having a bulk reflectance of substantially greater than or equal to 70% at the first wavelength of radiation. The material has a melting point above 1000° C.

Abstract: A reflector includes a multi layer mirror structure configured to reflect radiation at a first wavelength, and one or more additional layers. The absorbance and refractive index at a second wavelength of the multi layer mirror structure and the one or more additional layers, and the thickness of the multi layer mirror structure and the one or more additional layers, are configured such that radiation of the second wavelength which is reflected from a surface of the reflector interferes in a destructive manner with radiation of the second wavelength which is reflected from within the reflector.

Abstract: According to an aspect of the present invention, a spectral purity filter includes an aperture, the aperture being arranged to diffract a first wavelength of radiation and to allow at least a portion of a second wavelength of radiation to be transmitted through the aperture, the second wavelength of radiation being shorter than the first wavelength of radiation, wherein the aperture has a diameter greater than 20 ?m.

Abstract: An optical element includes a first layer that includes a first material, and is configured to be substantially reflective for radiation of a first wavelength and substantially transparent for radiation of a second wavelength. The optical element includes a second layer that includes a second material, and is configured to be substantially absorptive or transparent for the radiation of the second wavelength. The optical element includes a third layer that includes a third material between the first layer and the second layer, and is substantially transparent for the radiation of the second wavelength and configured to reduce reflection of the radiation of the second wavelength from a top surface of the second layer facing the first layer. The first layer is located upstream in the optical path of incoming radiation with respect to the second layer in order to improve spectral purity of the radiation of the first wavelength.

Abstract: Spectral purity of a radiation beam of a first wavelength may be improved by providing an optical element that includes a structure having at least first layer including a first material, which structure is configured to be substantially reflective for a radiation of the first wavelength and substantially transparent or absorptive for a radiation of a second wavelength, a second layer including a second material, the second layer being configured to be substantially reflective, absorptive or scattering for the radiation of the second wavelength, and vacuum between the first layer and the second layer, wherein the first layer is located upstream in the optical path of incoming radiation with respect to the second layer.

Abstract: A radiation source may include a radiation emitter for emitting radiation, a collector for collecting radiation emitted by the radiation emitter, and an outlet configured, in use, to introduce a cooled gas into the radiation source.

Abstract: A radiation source includes a radiation emitter configured to emit radiation, a collector configured to collect the radiation, and a contamination trap configured to trap contamination emitted by the radiation source. The contamination trap includes a plurality of foils that extend substantially radially, a first magnet ring configured to lie outside of an outer conical trajectory of radiation that is collected by the collector, and a second magnet ring configured to lie within the trajectory of radiation that is collected by the collector. The magnet rings are configured to provide a magnetic field that includes a component that is parallel to the foils.

Abstract: A debris prevention system is constructed and arranged to prevent debris emanating from a radiation source from propagating with radiation from the radiation source into or within a lithographic apparatus. The debris prevention system includes a first foil trap that is rotatable around an axis of rotation, and a second foil trap that at least partly encloses the first foil trap. The second foil trap includes a plurality of foils optically open respective to a central location for placement of a radiation source and optically closed respective to directions perpendicular to the axis of rotation.

Abstract: A spectral purity filter, in particular for use in a lithographic apparatus using EUV radiation for the projection beam, includes a plurality of apertures in a substrate. The apertures are defined by walls having side surfaces that are inclined to the normal to a front surface of the substrate.

Abstract: A method for manufacturing a spectral purity filter is provided in which openings in a first surface of a base material, corresponding to a plurality of apertures of the spectral purity filter, are formed. At least the surfaces of the base material surrounding the openings in the first surface are chemically treated to form a layer of a second material, and the base material is etched from the second surface such that the openings extend from the first surface of the base material to the second surface of the base material.

Abstract: A method of forming a spectral purity filter having a plurality of apertures configured to transmit extreme ultraviolet radiation and suppress transmission of a second type of radiation, in which trenches are formed in a base material in a pattern corresponding to the walls to be formed between the apertures. The trenches are filled with a grid material to form walls of the grid material, and the base material is selectively removed until the grid material is exposed and forms the spaces between the walls of the grid material for the apertures.