Detection of blocked water supply channels in a lithographic immersion apparatus

摘要

To ensure the correct functioning of an immersion hood in a lithographic immersion apparatus it is important that none of the holes in such an immersion hood for suppling and/or extracting the immersion liquid (such as for example ultra-pure water) or for suppling and/or extracting gas (such as for example CO_2) are blocked. Existing technology to delect blocked holes includes, for example, a test setup where a pressure sensor on an X-Y table is used to delect blocked holes with gas as medium. However, a test applying such a test setup can only be performed before the immersion hood is build-in into the lithographic immersion apparatus (at the site of the manufacturer of the immersion hood or during assembly of the lithographic immersion apparatus).