Patent ID: 7095499
Filing Date: 2006-08-22
Classification: G03F

Abstract:
1. A lithographic projection apparatus, comprising: an illumination system configured to provide a beam of radiation; a support configured to support a patterning device, the patterning device being configured to pattern the beam of radiation, and the patterning device being provided with a reference alignment mark having a first period; a substrate table configured to hold a substrate, the substrate being provided with a substrate alignment mark having a second period, the second period being smaller than the first period, the substrate being at least partially coated with a resist layer, the resist layer being provided with an additional alignment mark having a third period; a projection system configured to project the patterned beam of radiation onto a target portion of the substrate; and an alignment measuring system configured to: measure alignment of the substrate alignment mark with respect to the reference alignment mark by illuminating the substrate alignment mark with an alignment beam; image the substrate alignment mark on the reference alignment mark; upon illumination by the alignment beam of the substrate alignment mark, generate an interference pattern having a fourth period substantially equal to the first period; and image the interference pattern on the reference alignment mark, wherein the interference pattern is imaged on the reference alignment mark via an optical filter, the optical filter being configured to select diffraction orders of the radiation from the substrate alignment mark to proceed to said reference alignment mark.