An apparatus comprising at least one sealing aperture (40) comprising a hollow part (41), having an inner surface (42), extending at an interface between different zones (50;60) of the apparatus; and a member (43) positioned in the hollow part configured to substantially transmit EUV radiation and to substantially filter non-EUV radiation at the interface; wherein the inner surface of the hollow part has a surface treatment configured to increase absorption of the non-EUV radiation that is transferred by the member to the hollow part.

An extreme ultraviolet light generating system may include: a chamber; a target feeding unit configured to feed a target into the chamber; a drive laser unit configured to irradiate the target with a drive pulsed laser light beam to generate a plasma to thereby generate extreme ultraviolet light; a probe laser unit configured to irradiate the plasma with a probe pulsed laser light beam to thereby generate Thomson scattered light; a spectrometer configured to measure a spectrum waveform of an ionic term in the Thomson scattered light; and a wavelength filter disposed upstream of the spectrometer, and configured to suppress light with a predetermined wavelength from entering the spectrometer. The light with the predetermined wavelength may be part of light containing the Thomson scattered light, and the predetermined wavelength may be substantially same as a wavelength of the probe pulsed laser light beam.

Disclosed is a laser-driven photon source comprising drive optics which focus drive radiation so as to maintain a plasma. The point spread function of the drive optics has a point spread function (75) which is configured such that a spectral position of a peak output wavelength of a black body portion of output radiation emitted by said plasma within a desired wavelength band.

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.

A radiation system for controlling pulses of radiation comprising an optical element configured to interact with the pulses of radiation to control a characteristic of the pulses of radiation, an actuator configured to actuate the optical element according to a control signal received from a controller, the control signal at least partially depending on a reference pulse repetition rate of the radiation system and, a processor configured to receive pulse information from the controller and use the pulse information to determine an adjustment to the control signal. The radiation system may be used to improve an accuracy of a lithographic apparatus operating in a multi-focal imaging mode.

A laser apparatus includes a controller that selects one of a first gas control and a second gas control based on gas pressure measured by a pressure sensor. The first gas control causes at least one of first laser gas and second laser gas is supplied to a chamber such that the gas pressure in the chamber after the first gas control is higher than the gas pressure in the chamber before the first gas control. The second gas control causes at least the first laser gas is supplied to the chamber and causes a part of the laser gas in the chamber is exhausted such that a difference between the gas pressure in the chamber before the second gas control and the gas pressure in the chamber after the second gas control is smaller than a difference between the gas pressure in the chamber before the first gas control and the gas pressure in the chamber after the first gas control.

A pellicle having a metal oxysilicide layer. A pellicle having a molybdenum layer, a ruthenium layer and a silicon oxynitride layer, wherein the molybdenum layer is disposed between the ruthenium layer and the silicon oxynitride layer. A method of manufacturing a pellicle for a lithographic apparatus, the method including providing a metal oxysilicide layer. A lithographic assembly including a pellicle having a metal oxysilicide layer. The use of a pellicle having a metal oxysilicide layer in a lithographic apparatus.

A mask, a manufacturing method thereof, and a patterning method employing the mask. In the mask, a plurality of masks can be combined into one mask. The pattern area (01) of the mask is provided with a first pattern section (10) and a second pattern section (20) which are not overlapped with each other; light of a first wavelength can run through the first pattern section (10) but light of a second wavelength cannot run through the first pattern section; the light of the second wavelength can run thorough the second pattern section (20) but the light of the first wavelength cannot run through the second pattern section; and the light of the first wavelength and the light of the second wavelength can run through the non-pattern area, or any of the light of the first wavelength and the light of the second wavelength cannot run through the non-pattern area. The mask is obtained by combining a plurality of masks.

An method for generating illuminating radiation in an illumination apparatus for use in an inspection apparatus for use in lithographic processes is described. A driving radiation beam is provided that comprises a plurality of radiation pulses. The beam is split into first and second pluralities of driving radiation pulses. Each plurality of driving radiation pulses has a controllable characteristic. The first and second pluralities may be used to generate an illuminating radiation beam with an output wavelength spectrum. The first and second controllable characteristics are controlled so as to control first and second portions respectively of the output wavelength spectrum of the illuminating radiation beam.

A radiation driven light source comprises laser and focusing optics. These produce a beam of radiation focused on a plasma forming zone within a first container containing a gas (e.g. Xe). Collection optics collects photons emitted by a plasma maintained by the laser radiation to form a beam of output radiation. First container is enclosed within a hermetically sealed second container. Any ozone generated within the second container as a result of ultraviolet components of the output radiation is completely contained within the second container. Second container further filters out the ultraviolet components. Microwave radiation may be used instead of laser radiation to form the plasma.