Method for producing a mirror of a microlithographic projection exposure apparatus

A mirror of a microlithographic projection exposure apparatus comprising:

• a first mirror part;
• a second mirror part;
• an optical surface configured to reflect light;
• wherein:
• the first mirror part and the second mirror part are durably connected to one another in a region of a first connecting surface of the first mirror part and a second connecting surface of the second mirror part by a heat treatment;
• and
• the mirror has, within a volume zone that overlaps laterally with the optical surface and extends in depth from the optical surface to 1 cm, an average zero crossing temperature that deviates from a predefined value by less than or equal to +/−1 K and wherein the predefined value decreases with increasing distance from the optical surface.

A method for producing a mirror of a microlithographic projection exposure apparatus, comprising:

• providing a first mirror part and a second mirror part such that the first mirror part and the second mirror part are in contact in a region of a first connecting surface of the first mirror part and a second connecting surface of the second mirror part,
• forming a durable connection between the first mirror part and the second mirror part by heating the first mirror part and the second mirror part to a holding temperature of at least 400° C. and holding the first mirror part and second mirror part at the holding temperature during a holding time,
• after the holding time has elapsed, cooling the first mirror part and the second mirror part to a first cooling temperature at a first cooling rate of less than or equal to 100 K/h;
• and
• after the cooling to the first cooling temperature, cooling the first mirror part and the second mirror part to a second cooling temperature that is less than the first cooling temperature at a second cooling rate that is greater than the first cooling rate,
• wherein cooling the first mirror part and the second mirror part to the first cooling temperature and the second cooling temperature comprises cooling the first mirror part and the second mirror part such that a sliding average value of the cooling rate, formed over a temperature interval of 20 K, has an identical relative variation over time in a temperature range from 900° C. to 700° C., except for a deviation of less than or equal to 2 K/h, in an entire volume of the first mirror part and/or the second mirror part.