Disclosed is an optical component, being configured to function as an optical frequency converter in a broadband radiation source device. The optical component comprises a gas cell, and a hollow-core photonic crystal fiber at least partially enclosed within said gas cell. The local cavity volume of said gas cell, where said hollow-core photonic crystal fiber is enclosed within the gas cell, comprises a maximum value of 36 cm.sup.3 per cm of length of said hollow-core photonic crystal fiber.

Disclosed is a metrology apparatus for use in a lithographic manufacturing process. The metrology apparatus comprises a radiation source comprising a drive laser having an output split into a plurality of optical paths, each comprising a respective broadband light generator. The metrology apparatus further comprises illumination optics for illuminating a structure, at least one detection system for detecting scattered radiation, having been scattered by the structure and a processor for determining a parameter of interest of the structure from the scattered radiation.

The present invention provides a measurement apparatus that measures a position of an object, including an illumination system configured to illuminate the object with illumination light, an image forming system configured to form, on a photoelectric conversion device configured to detect an image of the object, an image of detected light from the object, and a separation system including a reflective polarizer and a /4 plate arranged between the illumination system and the image forming system, and configured to separate the illumination light and the detected light via the reflective polarizer and the /4 plate, wherein the separation system includes at least one optical member arranged between the reflective polarizer and the /4 plate, and each of the illumination system and the image forming system includes a transmission polarizer.

An optical system for improving alignment measurement accuracy is discussed. The optical system includes first and second optical elements. The first optical element may be configured to change a first beam having a first polarization state into a second beam having a second polarization state. The second optical element may be configured to provide total internal reflection of the second beam and to change the second beam into a third beam having a third polarization state. The first, second, and third polarization states may be different from each other.

An apparatus for determining a characteristic of a feature of an object comprises: a measurement radiation source; a measurement radiation delivery system; a measurement system; a pump radiation source; and a pump radiation delivery system. The measurement radiation source is operable to produce measurement radiation and the measurement radiation delivery system is operable to irradiate at least a part of a top surface of the object with the measurement radiation. The measurement system is operable to receive at least a portion of the measurement radiation scattered from the top surface and is further operable to determine a characteristic of the feature of the object from at least a portion of the measurement radiation scattered from the top surface. The pump radiation source is operable to produce pump radiation and the pump radiation delivery system is operable to irradiate at least a part of the top surface of the object with the pump radiation so as to produce a mechanical response (for example an acoustic wave) in the object.

A supercontinuum radiation source for an alignment mark measurement system comprises: a radiation source; illumination optics; a plurality of waveguides; and collection optics. The radiation source is operable to produce a pulsed radiation beam. The illumination optics is arranged to receive the pulsed pump radiation beam and to form a plurality of pulsed sub-beams, each pulsed sub-beam comprising a portion of the pulsed radiation beam. Each of the plurality of waveguides is arranged to receive at least one of the plurality of pulsed sub-beams beam and to broaden a spectrum of that pulsed sub-beam so as to generate a supercontinuum sub-beam. The collection optics is arranged to receive the supercontinuum sub-beam from each of the plurality of waveguides and to combine them so as to form a supercontinuum radiation beam.

A spectrally broadened radiation apparatus, including a laser configured to emit, through an output of the laser, radiation substantially only in the visible region of the electromagnetic spectrum, the radiation having a nominal wavelength, and an optical fiber optically coupled to the output of the laser, the optical fiber having an input to receive the radiation from the laser and having an output to provide spectrally broadened output radiation, the optical fiber configured to spectrally broaden the radiation from the laser to a spectral width of at least 0.5 nm around the nominal wavelength.

An alignment system (100) and method for positioning and/or keeping a first object (1) at a controlled distanced (D1) with respect to a second object (2). An object stage (11) is configured to hold a surface (1a) of the first object (1) at a distance (D1) over a surface (2a) of the second object (2). A sensor device (31) comprising a probe tip (31a) is connected at a predetermined probe level distance (Dp) relative to the surface (1a) of the first object (1). The probe tip (31a) is configured to perform an atomic force measurement (AFM) of a force (F1) exerted via the probe tip (31a) on a surface (2a) of the second object (2). A controller (80) is configured to control an object stage actuator (21) as a function of the probe level distance (Dp) and the measured force (F1) to maintain the controlled distanced (D1).

The present invention provides a measurement apparatus including a first filter unit including a plurality of first filters, and each configured to allow light having a different wavelength band to pass, a second filter unit including a plurality of second filters, and each configured to reduce light intensity of light and allow the light to pass, an obtaining unit configured to obtain data representing a transmittance of each of the plurality of second filters for a wavelength band of light having passed through each of the plurality of first filters, and a selection unit configured to select, based on the data obtained by the obtaining unit, from the plurality of second filters, one second filter arranged on an optical path together with one first filter among the plurality of first filters.

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.