Patent ID: 7750319
Filing Date: 2010-07-06
Classification: G01N,G03F

Abstract:
1. A method of measuring contamination of a lithographical element comprising: providing a process chamber with a first lithographical element, a second lithographical element, and a contaminant therein; covering part of the first lithographical element, thus providing a reference region on the first lithographical element being the covered part of the first lithographical element and a test region on the first lithographical element being the uncovered part of the first lithographical element; directing an exposure beam via the test region of the first lithographical element towards the second lithographical element such that at least one of the lithographical elements gets contaminated by the contaminant; uncovering the covered part of the first lithographical element, thus providing an uncovered reference region; and optically measuring the level of contamination of the at least one contaminated lithographical element in the process chamber.