Illumination assembly, method for providing a radiation beam, lithographic projection apparatus and device manufacturing method

A lithographic apparatus comprising:

• an illumination system to condition a projection beam of radiation, the illumination system comprising a beam expander arranged to receive a radiation beam directed in a first direction (z) and to expand the beam with a first magnification factor, Mx, in a second direction (x) and with a second magnification factor, My, in a third direction (y), the second and third directions being substantially mutually perpendicular and substantially perpendicular to the first direction, the expander being adjustable to change at least one of Mx and My;
• and
• a beam splitter that is arranged to split the radiation beam into two split radiation beams in at least one of the second and third direction, a propagation direction of the split radiation beams being substantially in the first direction, and to deliver the split radiation beams to the beam expander;
• a support to support a patterning device, the patterning device serving to impart the projection beam with a pattern in its cross-section;
• a substrate table to hold a substrate;
• and
• a projection system to project the patterned beam onto a target portion of the substrate.

A method comprising:

• providing a radiation beam propagating in a first direction (z);
• expanding the radiation beam using a beam expander by a first magnification factor Mx in a second direction (x) and by a second magnification factor My in a third direction (y), the second and third directions being substantially mutually perpendicular and substantially perpendicular to the first direction, wherein at least one of Mx and My is adjustable;
• splitting the radiation beam into two split radiation beams in at least one of the second and third direction, the propagation direction of the split radiation beams being substantially in the first direction;
• and
• delivering the split radiation beams to the beam expander.

A method for adjusting a beam splitter comprising:

• splitting a beam of radiation having a direction of propagation (z) into a pair of split radiation beams;
• determining divergences (divx, divy), of the pair of split radiation beams in substantially mutually orthogonal directions, x and y, respectively, wherein x and y are each substantially orthogonal to the z direction;
• determining which one of the divergences has the larger value and which has the smaller;
• determining an absolute difference between the values of the divergences;
• determining a distance in between the split radiation beams in the x and y direction;
• and
• adjusting the beam splitter in accordance with the determined distance, for reducing the difference between the divergences (divx, divy).

A device manufacturing method comprising:

• transmitting a beam of radiation in a first direction (z) using an illumination system;
• expanding the radiation beam using a beam expander by a first magnification factor Mx in a second direction (x) and by a second magnification factor My in a third direction (y), the second and third directions being substantially mutually perpendicular and substantially perpendicular to the first direction, wherein at least one of Mx and My is adjustable;
• splitting the radiation beam into two split radiation beams in at least one of the second and third direction, the propagation direction of the split radiation beams being substantially in the first direction;
• delivering the split radiation beams to the beam expander;
• patterning the beam with a pattern in its cross-section;
• and
• projecting the patterned beam of radiation onto a target portion of a substrate.