Abstract: Degradation of the reflectivity of one or more reflective optical elements in a system for generating EUV radiation is reduced by the controlled introduction of a gas into a vacuum chamber containing the optical element. The gas may be added to the flow of another gas such as hydrogen or alternated with the introduction of hydrogen radicals.

Abstract: Degradation of the reflectivity of one or more reflective optical elements in a system for generating EUV radiation is reduced by the controlled introduction of a gas into a vacuum chamber containing the optical element. The gas may be added to the flow of another gas such as hydrogen or alternated with the introduction of hydrogen radicals.

Abstract: A lithographic system comprises a radiation source and a lithographic apparatus. The radiation source provides radiation to the lithographic apparatus. The lithographic apparatus uses the radiation for imaging a pattern onto multiple target areas on a layer of photo-resist on a semiconductor substrate. The imaging requires a pre-determined dose of radiation. The system is controlled so as to set a level of a power of the radiation in dependence on a magnitude of the pre-determined dose.

Abstract: Degradation of the reflectivity of one or more reflective optical elements in a system (SO) for generating EUV radiation is reduced by the controlled introduction of a gas into a vacuum chamber (26) containing the optical element. The gas may be added to the flow of another gas such as hydrogen or alternated with the introduction of hydrogen radicals.

Abstract: Degradation of the reflectivity of one or more reflective optical elements in a system (SO) for generating EUV radiation is reduced by the controlled introduction of a gas into a vacuum chamber (26) containing the optical element. The gas may be added to the flow of another gas such as hydrogen or alternated with the introduction of hydrogen radicals.

Abstract: A radiation collector comprising a first collector segment comprising a plurality of grazing incidence reflector shells configured to direct radiation to converge in a first location at a distance from the radiation collector, a second collector segment comprising a plurality of grazing incidence reflector shells configured to direct radiation to converge in a second location at said distance from the radiation collector, wherein the first location and the second location are separated from one another.

Abstract: A radiation source for generating EUV radiation includes a laser configured to fire laser pulses at a target area to which is supplied a stream of fuel droplets, which may be tin droplets that emit EUV radiation when excited by the laser beam. The EUV radiation is collected by a collector. The tin droplets may be pre-conditioned by a laser pre-pulse before the main laser pulse to change the shape of the droplets so that the droplets are in an optimum condition for receiving the main laser pulse. Embodiments of the invention take into account the effect of the vaporization of one fuel droplet on succeeding droplets and allow the timing of the main and/or pre-pulse to be adjusted to take into account any delay in arrival of the subsequent droplet or oscillations in the shape of the subsequent droplet which may be caused by vaporization of the preceding droplet.

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: 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 analyzing 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: 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: A radiation source (e.g., LPP—laser produced plasma source) for generation of extreme UV (EUV) radiation has at least two fuel particle streams having different trajectories. Each stream is directed to cross the path of an excitation (laser) beam focused at a plasma formation region, but the trajectories are spaced apart at the plasma formation region, and the streams phased, so that only one stream has a fuel particle in the plasma formation region at any time, and so that when a fuel particle from one stream is generating plasma and EUV radiation at the plasma generation region, other fuel particles are sufficiently spaced so as to be substantially unaffected by the plasma. The arrangement permits potential doubling of the radiation intensity achievable for a particular fuel particle size.

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 collector comprising a first collector segment comprising a plurality of grazing incidence reflector shells configured to direct radiation to converge in a first location at a distance from the radiation collector, a second collector segment comprising a plurality of grazing incidence reflector shells configured to direct radiation to converge in a second location at said distance from the radiation collector, wherein the first location and the second location are separated from one another.

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 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 radiation source (e.g., LPP— laser produced plasma source) for generation of extreme UV (EUV) radiation has at least two fuel particle streams having different trajectories. Each stream is directed to cross the path of an excitation (laser) beam focused at a plasma formation region, but the trajectories are spaced apart at the plasma formation region, and the streams phased, so that only one stream has a fuel particle in the plasma formation region at any time, and so that when a fuel particle from one stream is generating plasma and EUV radiation at the plasma generation region, other fuel particles are sufficiently spaced so as to be substantially unaffected by the plasma. The arrangement permits potential doubling of the radiation intensity achievable for a particular fuel particle size.

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 radiation source for generating EUV radiation includes a laser configured to fire laser pulses at a target area to which is supplied a stream of fuel droplets, which may be tin droplets that emit EUV radiation when excited by the laser beam. The EUV radiation is collected by a collector. The tin droplets may be pre-conditioned by a laser pre-pulse before the main laser pulse to change the shape of the droplets so that the droplets are in an optimum condition for receiving the main laser pulse. Embodiments of the invention take into account the effect of the vaporization of one fuel droplet on succeeding droplets and allow the timing of the main and/or pre-pulse to be adjusted to take into account any delay in arrival of the subsequent droplet or oscillations in the shape of the subsequent droplet which may be caused by vaporization of the preceding droplet.

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: 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.