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.

An apparatus for generating extreme ultraviolet (EUV) light includes a raw material supply unit supplying a plasma source for generating EUV light. An EUV light source unit uses a laser to generate plasma from the plasma source. A filter is configured to extract EUV light from the light. A first protective layer is disposed on a front surface of the filter. A frame having a first region exposing at least a portion of the filter or the first protective layer is disposed on the first protective layer. A width of the first region is smaller than a width of the first protective layer and smaller than or equal to a width of the filter.

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 wavelength conversion system according to an aspect of the present disclosure includes a first crystal holder holding a first non-linear crystal, a second crystal holder holding a second non-linear crystal, a third crystal holder holding a third non-linear crystal, and a container housing the holders. The container has an entrance window and an emission window. The first non-linear crystal, the second non-linear crystal, and the third non-linear crystal are disposed in this order on an optical path of a laser beam traveling from the entrance window to the emission window. The crystal holders are rotatable. A first rotational axis that is a rotational axis of the first crystal holder is orthogonal to a second rotational axis that is a rotational axis of the second crystal holder, and the first rotational axis is parallel to a third rotational axis that is a rotational axis of the third crystal holder.

A wavelength conversion apparatus according to an aspect of the present disclosure is a wavelength conversion apparatus that performs wavelength conversion of light through a non-linear crystal and including a first non-linear crystal, a container in which the first non-linear crystal is housed, a crystal holding member provided inside the container for fixing the first non-linear crystal, a first window provided to the container for guiding light to the first non-linear crystal from outside of the container, a second window provided to the container for guiding light output from the first non-linear crystal to outside of the container, a first heater provided inside the container for heating the first non-linear crystal, a battery that supplies electric power to the first heater, and a first controller that controls electric power supply to the first heater.

A method is performed for scheduling a calibration relating to an optical device in a light source. The method can be performed by a calibration system including a calibration apparatus and a prediction controller. The method includes: receiving a property associated with the optical device while the optical device is being calibrated; calculating a current degradation metric based at least on the optical device property, the degradation metric modeling behavior of the optical device; estimating when a degradation of the optical device would exceed a threshold based on the current degradation metric; and scheduling a calibration of the optical device based at least in part on the estimate of optical device degradation.

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).

An apparatus for receiving input radiation and broadening a frequency range of the input radiation to provide broadband output radiation. The apparatus includes a chamber, a fiber, a gas generating apparatus, and a radical generating apparatus. The fiber includes a hollow core configured to guide radiation propagating through the fiber, the hollow core in fluid communication with the chamber. The gas generating apparatus is configured to provide a gas within the chamber. The radical generating apparatus is configured to provide free radicals within the chamber to reduce contaminants in the gas. The apparatus may be included in a radiation source.

A radiation measurement system (200) comprising an optical apparatus (205) configured to receive a radiation beam (210) and change an intensity distribution of the radiation beam to output a conditioned radiation beam (215), and a spectrometer (220) operable to receive the conditioned radiation beam and determine spectral content of the conditioned radiation beam. The radiation measurement system may form part of a lithographic apparatus.

An apparatus for generating extreme ultraviolet (EUV) light includes a raw material supply unit supplying a plasma source for generating EUV light. An EUV light source unit uses a laser to generate plasma from the plasma source. A filter is configured to extract EUV light from the light. A first protective layer is disposed on a front surface of the filter. A frame having a first region exposing at least a portion of the filter or the first protective layer is disposed on the first protective layer. A width of the first region is smaller than a width of the first protective layer and smaller than or equal to a width of the filter.