Device and method for treating the surface of an optical element of a lithography system in an atomic layer depositon process or an atomic layer etching process

A method of processing of a surface of an optical element of a lithography apparatus, in an atomic layer processing operation, said method comprising:

• arranging the optical element on a sample holder,
• positioning a processing head opposite the surface of the optical element, such that a first supply outlet of the processing head is disposed opposite a processing region on the surface,
• moving the processing head and/or the optical element such that the first supply outlet is moved across the processing region, wherein, during the movement, via the first supply outlet, a first precursor fluid is supplied to the processing region,
• moving the processing head and/or the optical element, such that a cleaning arrangement of the processing head is moved across the processing region, wherein the cleaning arrangement is configured to remove excess first precursor fluid from the processing region, and
• moving the processing head and/or the optical element such that a second supply outlet of the processing head is moved across the processing region, wherein, during the movement, via the second supply outlet, a second precursor fluid is supplied to the processing region,
• wherein the first and the second precursor fluids are selected to perform an atomic layer deposition process or an atomic layer etching process in the processing region, and wherein the first and/or the second precursor fluid is a liquid, wherein the respective precursor fluid, which is a liquid, is in the liquid state under process conditions under which the atomic layer processing operation is conducted and is contacted onto the surface of the optical element by the respective supply outlet in the liquid state.