A lithographic apparatus including a projection system having an optical axis and configured to project a radiation beam. The apparatus includes a measurement unit arranged to measure the radiation beam projected by the projection system, the measurement unit having an opening through which the radiation beam passes in use, and a sensing surface extending transverse to the optical axis and arranged to measure the radiation beam passing through the opening. The apparatus is configured to move the sensing surface in a plane transverse to the optical axis between a plurality of measurement positions. The radiation beam defines a view in the plane, and the measurement unit is configured such that the sensing surface captures, in each measurement position, a portion of the view smaller than 100% of the view.

A method for inspecting an extreme ultraviolet (EUV) light source includes: removing a collector mirror of the EUV light source from a collector chamber; installing an inspection apparatus within the collector chamber, the apparatus including a selectively extendable and retractable member and a camera at one end of the member; operating a first actuator to extend the member along a path through the interior chamber of the EUV light source, thereby moving the camera to a given position within the interior chamber of the EUV light source; operating a second actuator to pan the camera about an axis of rotation, thereby establishing a given camera orientation within the interior of the EUV light source; and, capturing an image of the interior chamber of the EUV light source with the camera while the camera is at the given position and orientation established by the operation of the first and second actuators.

A pupil stop serves for use in an illumination optical unit of a metrology system for determining, as a result of illumination and imaging under illumination and imaging conditions corresponding to those of an optical production system, an aerial image of an object to be measured. The pupil stop has two pole passage openings for specifying a respective pole of an illumination of the illumination optical unit specified by the pupil stop. In each case at least one stop web passes through the respective pole passage opening and consequently divides the pole passage opening into a plurality of partial pole openings. This yields a pupil stop with which an accuracy of a convergence of the illumination and imaging conditions of the optical production system to the illumination and imaging conditions of the optical measurement system can be improved.

Systems for cleaning optical surfaces of overlay inspection systems are disclosed. In particular, systems for optical-path coupling of light for in-situ photochemical cleaning in projection imaging systems are disclosed. A system for cleaning optical surfaces of overlay inspection systems includes a first illumination source, a detector, a set of illumination optics, and a set of imaging optics. In some embodiments, the system may include at least one of a second illumination source and a third illumination source, each of which may be configured to cause or aid the removal of contaminants from one or more optical surfaces of the system.

Disclosed is an illumination system for delivering incoherent radiation to a metrology sensor system. Also disclosed is an associated metrology system and method. The illumination system comprises a spatial filter system for selective spatial filtering of a beam of said incoherent radiation outside of a module housing of the metrology sensor system. At least one optical guide is provided for guiding the spatially filtered beam of incoherent radiation to the metrology sensor system, the at least one optical guide being such that the radiation guided has a substantially similar output angle as input angle.

A radiometer probe for matching a spectral sensitivity of a dry-film resist is provided. The radiometer probe includes a light probe and a filter-diffuser assembly connected to the light probe. The filter-diffuser assembly includes a filter housing configured to receive an optical diffuser positioned on a filter. The optical diffuser and the filter are separated by a spacer.

A movable body apparatus has: a substrate holder holding a substrate and can move in the X and Y-axes directions; a Y coarse movement stage movable in the Y-axis direction; a first measurement system acquiring position information on the substrate holder by heads on the substrate holder and a scale on the Y coarse movement stage; a second measurement system acquiring position information on the Y coarse movement stage by heads on the Y coarse movement stage and a scale; and a control system controlling the position of the substrate holder based on position information acquired by the first and second measurement systems. The first measurement system irradiates a measurement beam while moving the heads in the X-axis direction with respect to the scale, and the second measurement system irradiates a measurement beam while moving the heads in the Y-axis direction with respect to the scale.

A method to detect a defect on a lithographic sample includes the following steps: detection light and a detector having at least one sensor pixel are provided. Further, a detection pattern is provided causing a light structure of the detection light being structured at least along one dimension (1D, x). The detection pattern is aligned such that the detector is aligned normal to an extension (xy) of the light structure. Further, a complimentary pattern is provided having a 1D structure which is complimentary to that of the detection pattern. The sample is moved relative to the detection pattern while gathering the detection light on the detector. Further, a reference sample without defects or with negligible defects is provided. The reference sample also is moved relative to the detection pattern while gathering the detection light on the detector. A defect (s.sub.1 to s.sub.4) localization on the sample is decoded by correlation using the complementary pattern. Using such defect detection method improves a signal-to-noise ratio.

A vacuum system includes a wall of a vacuum chamber, a flange of the vacuum chamber, an outer seal disposed between the wall and the flange, and an inner seal disposed between the wall and the flange. The outer seal includes a first material; the inner seal includes a second material distinct from the first material. The inner seal is closer to the interior of the vacuum chamber than the outer seal and is separated from the outer seal by a gap. The outer seal may be capable of providing tighter vacuum sealing between the wall and the flange than the inner seal. The inner seal may be more resistant than the outer seal to a gas to be used to clean the interior of the vacuum chamber. The vacuum system also includes a path to couple the gap to a first vacuum pump, to evacuate the gap.

A lithographic apparatus including a projection system having an optical axis and configured to project a radiation beam. The apparatus includes a measurement unit arranged to measure the radiation beam projected by the projection system, the measurement unit having an opening through which the radiation beam passes in use, and a sensing surface extending transverse to the optical axis and arranged to measure the radiation beam passing through the opening. The apparatus is configured to move the sensing surface in a plane transverse to the optical axis between a plurality of measurement positions. The radiation beam defines a view in the plane, and the measurement unit is configured such that the sensing surface captures, in each measurement position, a portion of the view smaller than 100% of the view.