Radiation Source, Metrology Apparatus, Lithographic System and Device Manufacturing Method

An inspection apparatus for measuring a property of a structure on a substrate, the apparatus comprising:

• a support for the substrate having said structure thereon;
• an optical system configured to illuminate the structure under predetermined illumination conditions and to detect predetermined portions of radiation diffracted by the component target structures under said illumination conditions;
• a processor arranged to process information characterizing the detected radiation to obtain a measurement of said property of the structure,
• wherein said optical system includes a radiation source apparatus comprises,
• a container comprising walls configured to define a space that is configured to contain a gaseous medium in which plasma which emits plasma emitted radiation is generated following excitation of the gaseous medium by a driving radiation;
• and
• a thermal load applicator adapted to apply a thermal load to at least part of the walls of the container to reduce stresses in the walls.

A lithographic system comprising:

• a lithographic apparatus comprising:
• an illumination optical system arranged to illuminate a pattern;
• a projection optical system arranged to project an image of the pattern onto a substrate;
• and
• an inspection apparatus for measuring a property of a structure on a substrate, the apparatus comprising:
• a support for the substrate having said structure thereon;
• an optical system configured to illuminate the structure under predetermined illumination conditions and to detect predetermined portions of radiation diffracted by the component target structures under said illumination conditions;
• a processor arranged to process information characterizing the detected radiation to obtain a measurement of said property of the structure,
• wherein said optical system includes a radiation source apparatus comprises,
• a container comprising walls configured to define a space that is configured to contain a gaseous medium in which plasma which emits plasma emitted radiation is generated following excitation of the gaseous medium by a driving radiation;
• and
• a thermal load applicator adapted to apply a thermal load to at least part of the walls of the container to reduce stresses in the walls,
• wherein the lithographic apparatus is arranged to use the measurement results from the inspection apparatus in applying the pattern to further substrates.

A method of measuring a property of structures that have been formed by a lithographic process on a substrate, the method comprising:

• illuminating said structures using output radiation of a radiation source apparatus, the radiation source comprising a container comprising walls for defining a space containing a gaseous medium in which plasma which emits plasma emitted radiation is generated following excitation of the gaseous medium by a driving radiation and a thermal load applicator applying a thermal load to at least part of the walls of the container to reduce stresses in the walls;
• detecting radiation diffracted by the structures;
• and
• determining from properties of said diffracted radiation one or more properties of the structure.

A method of manufacturing devices, comprising:

• applying a device pattern to a series of substrates using a lithographic process;
• inspecting at least one composite target structure formed as part of or beside said device pattern on at least one of said substrates using a method comprising:
• illuminating said structures using output radiation of a radiation source apparatus, the radiation source comprising a container comprising walls for defining a space containing a gaseous medium in which plasma which emits plasma emitted radiation is generated following excitation of the gaseous medium by a driving radiation and a thermal load applicator applying a thermal load to at least part of the walls of the container to reduce stresses in the walls;
• detecting radiation diffracted by the structures;
• and
• determining from properties of said diffracted radiation one or more properties of the structure, and
• controlling the lithographic process for later substrates in accordance with the result of the inspection method.