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.

A multilayer mirror (M) reflecting extreme ultraviolet (EUV) radiation from a first wavelength range in an EUV spectral region includes a substrate (SUB) and a stack of layers (SL). The stack of layers has layers having a low index material and layers having a high index material. The low index material has a lower real part of the refractive index than does the high index material at a given operating wavelength in the first wavelength range. The stack of layers also includes a spectral purity filter on the stack of layers. The spectral purity filter is effective as an anti-reflection layer for ultraviolet (UV) radiation from a second wavelength range in a UV spectral region to increase an EUV-UV-reflectivity ratio of the multilayer mirror. The spectral purity filter (SPF) includes a non-diffractive graded-index anti-reflection layer (GI-AR) effective to reduce reflectivity in the second wavelength range.

In situ dynamic protection of an optical element surface against degradation includes disposing the optical element in an interior of an optical assembly for the FUV/VUV wavelength range and supplying at least one volatile fluorine-containing compound (A, B) to the interior for dynamic deposition of a fluorine-containing protective layer on the surface. The protective layer (7) is deposited on the surface layer by layer via a molecular layer deposition process. The compound includes a fluorine-containing reactant (A) supplied to the interior in a pulsed manner. A further reactant (B) is supplied to the interior also in a pulsed manner. An associated optical assembly includes an interior in which a surface is disposed, and at least one metering apparatus (123) that supplies a reactant to the interior. The metering apparatus provides a pulsed supply of the compound as a reactant (A, B) for layer by layer molecular layer deposition.

An EUV reflective structure includes a substrate and multiple pairs of a Si layer and a Mo layer. The Si layer includes a plurality of cavities.

Disclosed are pellicles for use in extreme ultraviolet (EUV) lithography, the pellicles comprising silicon carbide nanostructures, and exhibiting high transmittance of EUV exposure light and high mechanical strength, as well as methods of using these pellicles.

An optical element for a lithographic apparatus, the optical element including an anchor layer selected to support a top layer having self-terminating growth in an operating lithographic apparatus or plasma containing environment. Also described is a method of manufacturing an optical element, the method including depositing a top layer on anchor layer via exposure to plasma, preferably electromagnetically induced plasma. Lithographic apparatuses including such optical elements are also described.

An improved method and apparatus for determination of the absolute coefficient of thermal expansion of materials, including ultralow expansion materials, utilizes a metrology frame that is regulated within a first narrow temperature range that varies by only a small fraction of a degree Celsius from a set point temperature (e.g., less than about 0.01° C. from the set point temperature), while the temperature of the sample is varied to determine the coefficient of thermal expansion over a larger temperature range (e.g., 30, 40 or 50° C.). The method and apparatus permit determination of the coefficient of thermal expansion of a material to levels approaching 10.sup.−9/° C.

A method for producing an optical element includes: providing a substrate (102), applying a layer system (103), wherein an optically effective surface (101) is formed and wherein the layer system has a layer (104) that is thermally deformable for manipulating the geometric shape of the optically effective surface, and applying a temperature field to the optical element while at least regionally heating the thermally deformable layer to above a specified operating temperature of the optical system. The thermally deformable layer is configured such that a deformation that is induced when the temperature field is applied is at least partially maintained after the optical element has cooled. Also disclosed is an optical element (400) that has an optically effective surface (401), a substrate (402), and a layer system (403) that has a reflection layer system (406), which includes a shape-memory alloy.

The invention relates to a method for determining the thickness of a contaminating layer and/or the type of a contaminating material on a surface (7) in an optical system, in particular on a surface (7) in an EUV lithography system, comprising: irradiating the surface (7) on which plasmonic nanoparticles (8a,b) are formed with measurement radiation (10), detecting the measurement radiation (10a) scattered at the plasmonic nanoparticles (8a,b), and determining the thickness of the contaminating layer and/or the type of the contaminating material on the basis of the detected measurement radiation (10a). The invention also relates to an optical element (1) for reflecting EUV radiation (4), and to an EUV lithography system.

Strontium tetraborate can be used as an optical material. Strontium tetraborate exhibits high refractive indices, high optical damage threshold, and high microhardness. The transmission window of strontium tetraborate covers a very broad range of wavelengths, from 130 nm to 3200 nm, making the material particularly useful at VUV wavelengths. An optical component made of strontium tetraborate can be incorporated in an optical system, such as a semiconductor inspection system, a metrology system, or a lithography system. These optical components may include mirrors, lenses, lens arrays, prisms, beam splitters, windows, lamp cells or Brewster-angle optics.