An optical illumination system guides EUV radiation between a source region of an EUV light source and an object field, in which an object to be imaged is arrangeable. The illumination system has at least two EUV mirror components which reflect the EUV radiation and sequentially guide the EUV radiation between the source region and the object field. An optical diffraction component for suppressing extraneous light radiation is arranged on each of the two EUV mirror components. The two optical diffraction components are designed to suppress different extraneous light wavelengths. A first of the two optical diffraction components, which is arranged on a first of the EUV mirror components, is a grating with at least one first structure depth. A second of the two optical diffraction components, which is arranged on a second of the EUV mirror components, is a grating with at least one second different structure depth. The result can be improved suppression of extraneous light.

A compound lens assembly and method for making a compound lens assembly useful for deep ultraviolet lithography are described. The compound lens assembly includes a first lens component having an optical surface bonded to an optical surface of a second lens component. The bonding at the interface can be achieved using a hydroxide catalysis bonding technique. The compound lens assembly and process for making same solve problems relating to constringence and/or inherent birefringence known for conventional optical elements used in deep ultraviolet lithography or inspection of wafers or reticles in the DUV.

An apparatus includes a gas discharge system including a gas discharge chamber and configured to produce a light beam; and a spectral feature adjuster in optical communication with a pre-cursor light beam generated by the gas discharge chamber. The spectral feature adjuster includes: a body defining an interior that is held at a pressure below atmospheric pressure; at least one optical pathway defined between the gas discharge chamber and the interior of the body, the optical pathway being transparent to the pre-cursor light beam; and a set of optical elements within the interior, the optical elements configured to interact with the pre-cursor light beam.

A reflective optical element (17), in particular for reflecting EUV radiation (16), includes: a substrate (25), and a reflective coating (26) applied to the substrate (25). In one disclosed aspect, the substrate (25) is doped within its volume (V) with at least one precious metal (27). In a further disclosed aspect, the reflective coating (26) and/or a structured layer (28) that is formed between the substrate (25) and the reflective coating (26) is doped with at least one precious metal (27). Also disclosed are an optical arrangement, preferably a projection exposure apparatus for microlithography, in particular for EUV lithography, which includes at least one such reflective optical element (17), and a method of producing such a reflective optical element (17).

A transmissive diffraction grating for a phase-stepping measurement system for determining an aberration map for a projection system comprises an absorbing layer. The diffraction grating is for use with radiation having a first wavelength (for example (EUV radiation). The absorbing layer is provided with a two-dimensional array of through-apertures. The absorbing layer is formed from a material which has a refractive index for the radiation having the first wavelength in the range 0.% to 1.04.

In some embodiments, a reticle structure is provided. The reticle structure includes a reticle stage and a reticle mounted on the reticle stage. The reticle stage includes plural first burls and plural second burls, in which the second burls are disposed on a center of the reticle stage and the first burls disposed on an edge of the reticle stage such that the first burls surround the second burls. The reticle includes a base material and a pattern layer overlying the base material. The base material is secured on the first and second burls of the reticle stage. The pattern layer includes plural first gratings, and each of the first burls is vertically aligned with one of the first gratings.

A maskless, extreme ultraviolet (EUV) lithography scanner uses an array of microlenses, such as binary-optic, zone-plate lenses, to focus EUV radiation onto an array of focus spots (e.g. about 2 million spots), which are imaged through projection optics (e.g., two EUV mirrors) onto a writing surface (e.g., at 6× reduction, numerical aperture 0.55). The surface is scanned while the spots are modulated to form a high-resolution, digitally synthesized exposure image. The projection system includes a diffractive mirror, which operates in combination with the microlenses to achieve point imaging performance substantially free of geometric and chromatic aberration. Similarly, a holographic EUV lithography stepper can use a diffractive photomask in conjunction with a diffractive projection mirror to achieve substantially aberration-free, full-field imaging performance for high-throughput, mask-projection lithography. Maskless and holographic EUV lithography can both be implemented at the industry-standard 13.5-nm wavelength, and could potentially be adapted for operation at a 6.7-nm wavelength.

An overlay metrology target (T) is formed by a lithographic process. A first image (740(0)) of the target structure is obtained using with illuminating radiation having a first angular distribution, the first image being formed using radiation diffracted in a first direction (X) and radiation diffracted in a second direction (Y). A second image (740(R)) of the target structure using illuminating radiation having a second angular illumination distribution which the same as the first angular distribution, but rotated 90 degrees. The first image and the second image can be used together so as to discriminate between radiation diffracted in the first direction and radiation diffracted in the second direction by the same part of the target structure. This discrimination allows overlay and other asymmetry-related properties to be measured independently in X and Y, even in the presence of two-dimensional structures within the same part of the target structure.

Described is a metrology system for determining a characteristic of interest relating to at least one structure on a substrate, and associated method. The metrology system comprises a processor being configured to computationally determine phase and amplitude information from a detected characteristic of scattered radiation having been reflected or scattered by the at least one structure as a result of illumination of said at least one structure with illumination radiation in a measurement acquisition, and use the determined phase and amplitude to determine the characteristic of interest.

Methods for forming microstructures in photocurable material are described. At least one image of light or radiation for curing the photocurable material is applied in a pattern corresponding to the image. The image is formed by near-field diffraction of the light or radiation and comprises areas of higher intensity adjacent to areas of lower intensity.