EUV Collector

An EUV collector, comprising:

• a mirror surface which comprises surface structures configured to scatter a wavelength (λ) of EUV light,
• wherein:
• the mirror surface has a surface height with a spatial wavelength distribution between a lower limit spatial wavelength (PG) and an upper limit spatial wavelength;
• the lower limit spatial wavelength (PG) lies in the range between 1 μm and 100 μm;
• the upper limit spatial wavelength is at least ten times larger the lower limit spatial wavelength (PG);
• an effective roughness (rmsG) below the lower limit spatial wavelength (PG) satisfies the following relation:
• (4π rmsG cos(θ)/λ)2<0.1;
• where θ denotes an angle of incidence of the EUV light at the mirror surface;
• the following applies to an effective roughness (rmsGG′) between the lower limit spatial wavelength (PG) and the upper limit spatial wavelength (PG′):
• 1.5 rmsG<rmsGG′<6 rmsG;
• for the lower limit spatial wavelength (PG) of the spatial wavelength distribution the following relationship applies:
• PG≈(2 L/dIF)λ1/cos θ;
• where L is a distance between a mirror surface element carrying the surface structures and an intermediate focus into which a source region is transferred by the EUV collector during use;
• and
• dIF denotes a permissible diameter of the intermediate focus.

An illumination system, comprising:

• an EUV collector comprising a mirror surface which comprises surface structures configured to scatter a wavelength (λ) of EUV light;
• and
• an illumination optical unit configured to guide the EUV light from the EUV collector toward an object field in an object plane,
• wherein:
• the mirror surface has a surface height with a spatial wavelength distribution between a lower limit spatial wavelength and an upper limit spatial wavelength;
• the lower limit spatial wavelength lies in the range between 1 μm and 100 μm;
• the upper limit spatial wavelength is at least ten times larger than the lower limit spatial wavelength;
• an effective roughness (rmsG) below the lower limit spatial wavelength satisfies the following relation:
• (4π rmsG cos(θ)/λ)2<0.1;
• where θ denotes an angle of incidence of the EUV light at the mirror surface;
• the following applies to an effective roughness (rmsGG′) between the lower limit spatial wavelength (PG) and the upper limit spatial wavelength (PG′):
• 1.5 rmsG<rmsGG′<6 rmsG;
• and
• the EUV collector is arranged in near-field fashion in relation to a field plane that is conjugate to the object plane.