Abstract: Disclosed is a metrology apparatus and method for measurement of a diffractive structure on a substrate. The metrology apparatus comprises a radiation source operable to provide first radiation for excitation of the diffractive structure such that high harmonic second radiation is generated from said diffractive structure and/or substrate; and a detection arrangement operable to detect said second radiation, at least a portion of which having been diffracted by said diffractive structure.

Abstract: Disclosed is a metrology apparatus for measurement of a target formed on a substrate by a lithographic process and associated method. The metrology apparatus comprises a radiation source operable to provide first radiation; a configured solid high harmonic generation medium being configured to receive and be excited by said first radiation to generate high harmonic second radiation from an output surface of the configured solid high harmonic generation medium; and a detection arrangement operable to detect said second radiation, at least a portion of which having been scattered by said target. The configured solid high harmonic generation medium is configured to shape the beam of said second radiation and/or separate said first and second radiation.

Abstract: Disclosed is a wavefront sensor for measuring a wavefront of a radiation. The wavefront sensor comprises a mask comprising a pattern located in path of the radiation to interact with the radiation. The radiation impinging on the mask forms a radiation detection pattern on a radiation detector subsequent to the mask, and the pattern of the mask is designed at least partly based on a requirement of the radiation detection pattern.

Abstract: Disclosed is an illumination source comprising a gas delivery system being configured to provide a gas target for generating an emitted radiation at an interaction region of the gas target, and an interferometer for illuminating at least part of the gas target with an interferometer radiation to measure a property of the gas target.

Abstract: A high harmonic radiation source and associated method of generating high harmonic radiation is disclosed. The high harmonic radiation source is configured to condition a gas medium by irradiating the gas medium with a pre-pulse of radiation, thereby generating a plasma comprising a pre-pulse plasma distribution; and irradiate the gas medium with a main pulse of radiation to generate said high harmonic radiation. The conditioning step is such that the plasma comprising a pre-pulse plasma distribution acts to configure a wavefront of said main pulse to improve one or both of: the efficiency of the high harmonic generation process and the beam quality of the high harmonic radiation. The high harmonic radiation source further may comprise a beam shaping device configured to shape said customized pre-pulse prior to said conditioning.

Abstract: Disclosed is an illumination source comprising a gas delivery system comprising a gas nozzle. The gas nozzle comprises an opening in an exit plane of the gas nozzle. The gas delivery system is configured to provide a gas flow from the opening for generating an emitted radiation at an interaction region. The illumination source is configured to receive a pump radiation having a propagation direction and to provide the pump radiation in the gas flow. A geometry shape of the gas nozzle is adapted to shape a profile of the gas flow such that gas density of the gas flow first increases to a maximum value and subsequently falls sharply in a cut-off region along the propagation direction.

Abstract: An illumination source apparatus (500), suitable for use in a metrology apparatus for the characterization of a structure on a substrate, the illumination source apparatus comprising: a high harmonic generation, HHG, medium (502); a pump radiation source (506) operable to emit a beam of pump radiation (508); and adjustable transformation optics (510) configured to adjustably transform the transverse spatial profile of the beam of pump radiation to produce a transformed beam (518) such that relative to the centre axis of the transformed beam, a central region of the transformed beam has substantially zero intensity and an outer region which is radially outwards from the centre axis of the transformed beam has a non-zero intensity, wherein the transformed beam is arranged to excite the HHG medium so as to generate high harmonic radiation (540), wherein the location of said outer region is dependent on an adjustment setting of the adjustable transformation optics.

Abstract: Methods and corresponding apparatus operable to cause an interaction between a drive radiation beam and a medium for generation of emitted radiation by high harmonic generation, the arrangement comprising: an interaction region positioned at an interaction plane and configured to receive the medium; a beam block positioned upstream of the interaction plane at a beam block plane and configured to partially block the drive radiation beam; a beam shaper positioned upstream of the beam block plane at an object plane and configured to control a spatial distribution of the drive radiation beam; and at least one lens positioned upstream of the interaction plane and downstream of the beam block plane, wherein the lens being positioned such that an image of the spatial distribution of the drive radiation beam is formed at the interaction plane.

Abstract: An illumination source apparatus (500), suitable for use in a metrology apparatus for the characterization of a structure on a substrate, the illumination source apparatus comprising: a high harmonic generation, HHG, medium (502); a pump radiation source (506) operable to emit a beam of pump radiation (508); and adjustable transformation optics (510) configured to adjustably transform the transverse spatial profile of the beam of pump radiation to produce a transformed beam (518) such that relative to the centre axis of the transformed beam, a central region of the transformed beam has substantially zero intensity and an outer region which is radially outwards from the centre axis of the transformed beam has a non-zero intensity, wherein the transformed beam is arranged to excite the HHG medium so as to generate high harmonic radiation (540), wherein the location of said outer region is dependent on an adjustment N setting of the adjustable transformation optics.

Abstract: Methods and apparatus for directing onto a substrate a radiation beam emitted as a result of high harmonic generation (HHG).

Abstract: Methods and apparatus for directing onto a substrate a radiation beam emitted as a result of high harmonic generation (HHG).

Abstract: A metrology apparatus for determining a characteristic of interest of a structure on a substrate, the structure having diffractive properties, the apparatus comprising: focusing optics configured to focus illumination radiation comprising a plurality of wavelengths onto the structure; a first detector configured to detect at least part of the illumination radiation which has been diffracted from the structure; and additional optics configured to produce, on at least a portion of the first detector, a wavelength-dependent spatial distribution of different wavelengths of the illumination radiation which has been diffracted from the structure, wherein the first detector is arranged to detect at least a non-zero diffraction order of the illumination radiation which has been diffracted from the structure.

Abstract: An illumination source apparatus (500), suitable for use in a metrology apparatus for the characterization of a structure on a substrate, the illumination source apparatus comprising: a high harmonic generation, HHG, medium (502); a pump radiation source (506) operable to emit a beam of pump radiation (508); and adjustable transformation optics (510) configured to adjustably transform the transverse spatial profile of the beam of pump radiation to produce a transformed beam (518) such that relative to the centre axis of the transformed beam, a central region of the transformed beam has substantially zero intensity and an outer region which is radially outwards from the centre axis of the transformed beam has a non-zero intensity, wherein the transformed beam is arranged to excite the HHG medium so as to generate high harmonic radiation (540), wherein the location of said outer region is dependent on an adjustment setting of the adjustable transformation optics.

Abstract: Disclosed is a high harmonic generation (HHG) radiation source which may be used to generate measurement radiation for an inspection apparatus. In such a radiation source, a pump radiation source is operable to emit pump radiation at a high harmonic generation gas medium thereby exciting the high harmonic generation gas medium within a pump radiation interaction region so as to generate the high harmonic radiation and an ionization radiation source is operable to emit ionization radiation at the high harmonic generation gas medium to ionize a gas at an ionization region between the pump radiation interaction region and an optical output of the illumination source.

Abstract: Methods and corresponding apparatus operable to cause an interaction between a drive radiation beam and a medium for generation of emitted radiation by high harmonic generation, the arrangement comprising: an interaction region positioned at an interaction plane and configured to receive the medium; a beam block positioned upstream of the interaction plane at a beam block plane and configured to partially block the drive radiation beam; a beam shaper positioned upstream of the beam block plane at an object plane and configured to control a spatial distribution of the drive radiation beam; and at least one lens positioned upstream of the interaction plane and downstream of the beam block plane, wherein the lens being positioned such that an image of the spatial distribution of the drive radiation beam is formed at the interaction plane.

Abstract: Disclosed is gas delivery system which is suitable for a high harmonic generation (HHG) radiation source which may be used to generate measurement radiation for an inspection apparatus. In such a radiation source, a gas delivery element delivers gas in a first direction. The gas delivery element has an optical input and an optical input, defining an optical path running in a second direction. The first direction is arranged relative to the second direction at an angle that is not perpendicular or parallel. Also disclosed is a gas delivery element having a gas jet shaping device, or a pair of gas delivery elements, one of which delivers a second gas, such that the gas jet shaping device or second gas is operable to modify a flow profile of the gas such that the number density of the gas falls sharply.

Abstract: An illumination source apparatus (500), suitable for use in a metrology apparatus for the characterization of a structure on a substrate, the illumination source apparatus comprising: a high harmonic generation, HHG, medium (502); a pump radiation source (506) operable to emit a beam of pump radiation (508); and adjustable transformation optics (510) configured to adjustably transform the transverse spatial profile of the beam of pump radiation to produce a transformed beam (518) such that relative to the centre axis of the transformed beam, a central region of the transformed beam has substantially zero intensity and an outer region which is radially outwards from the centre axis of the transformed beam has a non-zero intensity, wherein the transformed beam is arranged to excite the HHG medium so as to generate high harmonic radiation (540), wherein the location of said outer region is dependent on an adjustment setting of the adjustable transformation optics.

Abstract: A free electron laser FEL comprises an undulator 24 generating coherent EUV radiation receiving an upstream electron beam EB2 and emitting a downstream electron beam EB4 and at least an electron source 21a, 21b operable to produce an upstream electron beam EB1, EB2 comprising bunches of electrons. A beam path is configured to direct the upstream electron beam through: a linear accelerator system (LINAC) comprising at least a first and a second linear accelerators 22a, 22b, a bunch compressor 28b, and said undulator 24.

Abstract: Methods and apparatus for generation of radiation by high harmonic generation, HHG. The apparatus comprises: a chamber for holding a vacuum, the chamber comprising a radiation input, a radiation output and an interaction region at which, in use, a medium is present, the chamber being arranged such that, in use, when driving radiation propagates through the radiation input and is incident upon the medium, the medium emits radiation via HHG, the emitted radiation propagating through the radiation output; and at least one plasma generator at the radiation input and/or the radiation output for generating a plasma volume allowing the driving radiation and emitted radiation, respectively, to propagate through the plasma volume.

Abstract: Disclosed is a high harmonic generation (HHG) radiation source which may be used to generate measurement radiation for an inspection apparatus. In such a radiation source, a pump radiation source is operable to emit pump radiation at a high harmonic generation gas medium thereby exciting the high harmonic generation gas medium within a pump radiation interaction region so as to generate the high harmonic radiation and an ionization radiation source is operable to emit ionization radiation at the high harmonic generation gas medium to ionize a gas at an ionization region between the pump radiation interaction region and an optical output of the illumination source.