Patent ID: 7927090

Claim:
An imprint lithography apparatus for imprinting a substrate having a first surface to be imprinted and a second surface opposite the first surface, the second surface having a substrate alignment marking, the apparatus comprising: a substrate table arranged to support the substrate, with the second surface of the substrate facing the substrate table; a template holder arranged to hold a template comprising a template alignment mark, the template arranged to imprint the first surface of the substrate; and an alignment system arranged to align the template alignment mark to the substrate alignment mark on the substrate; wherein the substrate table comprises a substrate table optical system located in an optical cavity within the substrate table to allow the substrate alignment mark to be viewed by the alignment system, the substrate table optical system comprising at least one lens arranged to focus an image of the substrate alignment mark adjacent to the template alignment mark; and wherein the alignment system comprises a radiation source arranged to provide an alignment beam of radiation through the substrate table optical system to illuminate the substrate alignment mark with the alignment beam of radiation, and a radiation detector arranged to receive a return radiation beam from the substrate alignment mark after the return radiation beam has passed through the substrate table optical system and through the template.