Beam delivery for EUV lithography

An EUV radiation system comprising:

• a laser apparatus configured to emit a main beam of radiation;
• a plasma generation site located at a position in which a fuel comes into contact with the main beam of radiation to form a plasma;
• and
• a beam delivery apparatus configured to direct the main beam of radiation from the laser apparatus to the plasma generation site, the beam delivery apparatus comprising:
• variable zoom optics configured to condition the main beam of radiation so as to output a conditioned beam having a configurable beam diameter;
• a plurality of mirrors configured to direct the conditioned beam to the plasma generation site;
• and
• a controller configured to control the variable zoom optics based on a size of a fuel droplet at the plasma generation site, wherein an axial position of the plasma generation site is different from a focus position of the conditioned beam.

A lithographic apparatus, comprising:

• a laser apparatus operably configured to emit a main beam of radiation;
• a plasma generation site located at a position in which a fuel will be contacted by the main beam of radiation to form a plasma;
• and
• a beam delivery apparatus configured to direct the main beam of radiation from the laser apparatus to the plasma generation site, the beam delivery apparatus comprising:
• variable zoom optics configured to condition the main beam of radiation so as to output a conditioned beam having a configurable beam diameter, the configurable beam diameter;
• a plurality of mirrors configured to direct the conditioned beam to the plasma generation site to form a beam of EUV radiation;
• and
• a controller configured to control the variable zoom optics based on a size of a fuel droplet at the plasma generation site, wherein an axial position of the plasma generation site is different from a focus position of the conditioned beam.

A method, comprising:

• passing a beam of radiation through variable zoom optics to obtain a conditioned beam having a configurable beam diameter;
• directing the condition beam a plasma generation site;
• and
• controlling the variable zoom optics based on a size of a fuel droplet at the plasma generation site, wherein an axial position of the plasma generation site is different from a focus position of the conditioned beam.