Patent ID: 8129097

Claim:
A method of obtaining information related to a defect present in the irradiation of a substrate coated with a layer of radiation sensitive material using immersion lithography, the method comprising: irradiating an area of the radiation sensitive material with a non-patterned radiation beam, the area being irradiated with a dose which is sufficient for the radiation sensitive material to be substantially removed during subsequent development of the radiation sensitive material if the radiation sensitive material is a positive radiation sensitive material, or with a dose which is sufficient for the radiation sensitive material to be substantially insoluble during subsequent development of the radiation sensitive material if the radiation sensitive material is a negative radiation sensitive material, such that a first part of the radiation sensitive material is sufficiently soluble for the part of the radiation sensitive material to be substantially removed during subsequent development and a second part of the radiation sensitive material is insoluble during subsequent development; developing the radiation sensitive material to remove the first part of the radiation sensitive material; and obtaining information at least indicative of the topography of the second part of the radiation sensitive material remaining on the substrate after the radiation sensitive material has been developed in order to obtain information related to the defect.