Device manufacturing method

摘要

In-situ cleaning of an optical component for use in a lithographic projection apparatus can be carried out by irradiating a space (2) within the apparatus containing the optical component (3) with UV or EUV radiation having a wavelength of less than 250nm, in the presence of molecular oxygen. Generally, the space will be purged with a purge gas which contains a small amount of molecular oxygen in addition to the usual purge gas composition. The technique can also be used in an evacuated space by introducing a low pressure of molecular oxygen into the space. This technique has the advantage that the use of unstable materials such as ozone is avoided.