An extreme ultra violet (EUV) light source apparatus includes a metal droplet generator, a collector mirror, an excitation laser inlet port for receiving an excitation laser, a first mirror configured to reflect the excitation laser that passes through a zone of excitation, and a second mirror configured to reflect the excitation laser reflected by the first mirror.

A reflector comprising a hollow body having an interior surface defining a passage through the hollow body, the interior surface having at least one optical surface part configured to reflect radiation and a supporter surface part, wherein the optical surface part has a predetermined optical power and the supporter surface part does not have the predetermined optical power. The reflector is made by providing an axially symmetric mandrel; shaping a part of the circumferential surface of the mandrel to form at least one inverse optical surface part that is not rotationally symmetric about the axis of the mandrel; forming a reflector body around the mandrel; and releasing the reflector body from the mandrel whereby the reflector body has an optical surface defined by the inverse optical surface part and a supporter surface part defined by the rest of the outer surface of the mandrel.

A reflector comprising a hollow body having an interior surface defining a passage through the hollow body, the interior surface having at least one optical surface part configured to reflect radiation and a supporter surface part, wherein the optical surface part has a predetermined optical power and the supporter surface part does not have the predetermined optical power. The reflector is made by providing an axially symmetric mandrel; shaping a part of the circumferential surface of the mandrel to form at least one inverse optical surface part that is not rotationally symmetric about the axis of the mandrel; forming a reflector body around the mandrel; and releasing the reflector body from the mandrel whereby the reflector body has an optical surface defined by the inverse optical surface part and a supporter surface part defined by the rest of the outer surface of the mandrel.

A radiation source apparatus includes a vessel, a laser source, a collector, and a reflective mirror. The vessel has an exit aperture. The laser source is at one end of the vessel and configured to excite a target material to form a plasma. The collector is disposed in the vessel and configured to collect a radiation emitted by the plasma and to direct the collected radiation to the exit aperture of the vessel. The reflective mirror is in the vessel and configured to reflect the laser beam toward an edge of the vessel.

A radiation source apparatus includes a vessel, a laser source, a collector, and a reflective mirror. The vessel has an exit aperture. The laser source is at one end of the vessel and configured to excite a target material to form a plasma. The collector is disposed in the vessel and configured to collect a radiation emitted by the plasma and to direct the collected radiation to the exit aperture of the vessel. The reflective mirror is in the vessel and configured to reflect the laser beam toward an edge of the vessel.

A method for producing a diffractive optical element and a diffractive optical element are disclosed. In an embodiment a method for producing a diffractive optical element includes generating a surface structure by implanting ions into a material of a substrate, a layer or a layer system, wherein the surface structure includes a structure height of less than 10 nm.

A method and a novel flexure interface apparatus are provided for ultrahigh-vacuum (UHV) applications for precision nanopositioning systems. An ultrahigh-vacuum (UHV) metrology base is integrated with an ultrahigh-vacuum (UHV) flange together including a precision and compact flexure interface structure defining a UHV metrology base near-zero-length feedthrough. The UHV metrology base is directly mounted to a flange mounting surface in air with nanopositioning and thermal stability. The precision and compact flexure interface structure has sufficient strength to hold the vacuum force and sufficiently flexible to survive with the thermal expansion stress during bakeout process.

A method and a novel flexure interface apparatus are provided for ultrahigh-vacuum (UHV) applications for precision nanopositioning systems. An ultrahigh-vacuum (UHV) metrology base is integrated with an ultrahigh-vacuum (UHV) flange together including a precision and compact flexure interface structure defining a UHV metrology base near-zero-length feedthrough. The UHV metrology base is directly mounted to a flange mounting surface in air with nanopositioning and thermal stability. The precision and compact flexure interface structure has sufficient strength to hold the vacuum force and sufficiently flexible to survive with the thermal expansion stress during bakeout process.

A method for in situ protection of a surface (7a) of an aluminum layer (7) of a VUV radiation reflecting coating (6) of an optical element (4), arranged in an interior of an optical arrangement, against the growth of an aluminum oxide layer (8), including carrying out an atomic layer etching process for layer-by-layer removal of the aluminum oxide layer from the surface. The etching process includes a surface modification step and a material detachment step. At least one boron halide is supplied as a surface modifying reactant to the interior in pulsed fashion during the surface modification step. A plasma is generated at a surface (8a) of the aluminum oxide layer, at least during the material detachment step. The atomic layer etching process is performed until the aluminum oxide layer reaches a given thickness (D), or the aluminum oxide layer is kept below that thickness (D) by the process.

A method for in situ protection of a surface (7a) of an aluminum layer (7) of a VUV radiation reflecting coating (6) of an optical element (4), arranged in an interior of an optical arrangement, against the growth of an aluminum oxide layer (8), including carrying out an atomic layer etching process for layer-by-layer removal of the aluminum oxide layer from the surface. The etching process includes a surface modification step and a material detachment step. At least one boron halide is supplied as a surface modifying reactant to the interior in pulsed fashion during the surface modification step. A plasma is generated at a surface (8a) of the aluminum oxide layer, at least during the material detachment step. The atomic layer etching process is performed until the aluminum oxide layer reaches a given thickness (D), or the aluminum oxide layer is kept below that thickness (D) by the process.