A reflective optical element (17), in particular for an illumination optical unit of a projection exposure apparatus includes: a structured surface (25a) that preferably forms a grating structure (29), and a reflective coating (36) that is applied to the structured surface (25a). The reflective coating (36) covers the structured surface (25a) discontinuously, and the reflective optical element (17) has at least one protective layer (37) that covers the structured surface (25a) continuously. Also disclosed are an illumination optical unit (4) for a projection exposure apparatus (1) including at least one reflective optical element (17) of this type, to a projection exposure apparatus (1) including an illumination optical unit (4) of this type, and to a method for producing a protective layer (37) on a reflective optical element (17) of this type.

An illumination optical apparatus illuminates a pattern on a mask with illumination light. The illumination optical apparatus includes an optical integrator arranged in an optical path of the illumination light, and a polarization member made of optical material with optical rotatory power, which is arranged in the optical path on an incidence side of the optical integrator, and which changes a polarization state of the illumination light. The illumination light from the polarization member is irradiated onto the pattern through a pupil plane of the illumination optical apparatus.

A collector mirror for an EUV microlithography system. The collector mirror includes an optical grating having an optically effective mirror surface, which reflects electromagnetic used rays in an EUV spectral range emanating from a first focal point and focuses them onto a second focal point. The first and second focal points lie on a side of the optical grating facing the mirror surface and define an optical axis. The optical grating is configured, in interaction with a stop arranged at the second focal point, to allow the used rays to pass through the stop and to block electromagnetic remaining rays in a remaining spectral range different than the EUV spectral range. The optical grating includes a blazed grating composed of a plurality of mirror facets, each having a facet surface. The facet surfaces form the mirror surface of the blazed grating.

An EUV collector mirror has a reflection surface (16) to reflect usable EUV light which impinges on the reflection surface (16) from a source region (17) to a subsequent EUV optics. The reflection surface (16) carries a pump light grating structure (19) configured to retroreflect pump light (22) which impinges upon the pump light grating structure (19) from the source region (17) back to the source region (17). The pump light (22) has a wavelength deviating from the wavelength of the usable EUV light. Such EUV collector mirror enables a high conversion efficiency between the energy of pump light of a laser discharged produced plasma (LDPP) EUV light source on the one hand and the resulting usable EUV energy on the other.

A detection apparatus that detects a position deviation between an original and a substrate is provided. The apparatus includes an illumination optical system configured to illuminate a first diffraction grating arranged on the original and a second diffraction grating arranged on the substrate, and a detection optical system configured to detect interference light formed by diffracted light diffracted by the first diffraction grating and diffracted light diffracted by the second diffraction grating. The illumination optical system performs dipole illumination by light including two poles in a pupil plane of the illumination optical system, and polarization directions of light beams emitted from the two poles, respectively, and incident on the substrate are orthogonal to each other.

A method of controlling a feedback system with a data matching module of an extreme ultraviolet (EUV) radiation source is disclosed. The method includes obtaining a slit integrated energy (SLIE) sensor data and diffractive optical elements (DOE) data. The method performs a data match, by the data matching module, of a time difference of the SLIE sensor data and the DOE data to identify a mismatched set of the SLIE sensor data and the DOE data. The method also determines whether the time difference of the SLIE sensor data and the DOE data of the mismatched set is within an acceptable range. Based on the determination, the method automatically validates a configurable data of the mismatched set such that the SLIE sensor data of the mismatched set is valid for a reflectivity calculation.

An optical diffraction component is configured to suppress at least one target wavelength by destructive interference. The optical diffraction component includes at least three diffraction structure levels that are assignable to at least two diffraction structure groups. A first of the diffraction structure groups is configured to suppress a first target wavelength λ.sub.1. A second of the diffraction structure groups is configured to suppress a second target wavelength λ.sub.2, where (λ.sub.1−λ.sub.2).sup.2/(λ.sub.1+λ.sub.2).sup.2<20%. A topography of the diffraction structure levels can be described as a superimposition of two binary diffraction structure groups. Boundary regions between adjacent surface sections of each of the binary diffraction structure groups have a linear course and are superimposed on one another at most along sections of the linear course.

Methods and apparatus for determining an intensity profile of a radiation beam. The method comprises providing a diffraction structure, causing a relative movement of the diffraction structure relative to the radiation beam from a first position, wherein the radiation beam does not irradiate the diffraction structure to a second position, wherein the radiation beam irradiates the diffraction structure, measuring, with a radiation detector, diffracted radiation signals produced from a diffraction of the radiation beam by the diffraction structure as the diffraction structure transitions from the first position to the second position or vice versa, and determining an intensity profile of the radiation beam based on the measured diffracted radiation signals.

An optical diffraction component has a periodic grating structure profile. The diffraction structure levels are arranged so that a wavelength range around two different target wavelengths diffracted by the grating structure profile has radiation components with three different phases that interfere destructively with one another. Diffraction structure levels predefine a topography of a grating period of the grating structure profile that is repeated regularly along a period running direction. These include a neutral diffraction structure level, a positive diffraction structure level raised relative thereto, and a negative diffraction structure level lowered relative thereto. The neutral diffraction structure level has an extent along the period running direction which is less than 50% of the extent of the grating period. A difference between the two target wavelengths is less than 50%. The result is an optical diffraction component whose possibilities for use can be extended, for example, to stray light suppression.

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.