Light collector mirror carrier

A method of carrying an extreme ultraviolet light source collector mirror, the method comprising:

• providing a carrier including:
• providing a front panel having an inner surface and an outer surface opposite the inner surface, and defining a single through opening that has an edge having a plurality of scallops, the scallops being positioned around a circumference of the edge and being separated by arcs, wherein the arcs define a circle that has a diameter that is less than a diameter of a circular boundary of a reflective surface of the collector mirror and that has a center that coincides with the center of the through opening;
• providing a back panel having an inner surface that faces the front panel and an outer surface opposite the inner surface;
• and
• providing a plurality of posts each having a flange;
• and
• securing an extreme ultraviolet light source collector mirror within the carrier, securing including:
• receiving a flat rim around the circular boundary of the collector mirror between the flanges of the posts and the arcs of the front panel;
• and
• connecting the back panel to the front panel using the posts to thereby sandwich the flat rim between the inner surface of the front panel and flanges of the posts and to enable cleaning agent to pass through and strike the reflective surface of the extreme ultraviolet light source collector mirror.