Patent ID: 8130360

Claim:
An exposure apparatus which comprises an original stage that holds an original, the original stage having a mark thereon, an illumination optical system which illuminates the original held by the original stage, a substrate stage that holds a substrate, and a projection optical system which projects a pattern of the original onto the substrate held by the substrate stage, the apparatus comprising: an image sensor that receives measurement light and produces an output; a measurement optical system configured to guide measurement light to obliquely enter the projection optical system, and further to guide the measurement light that is returned from the projection optical system to the image sensor; and a control unit configured to calculate surface position information of the substrate based on the output from the image sensor, wherein the image sensor senses: (i) an image of the mark arranged on the original stage, the image being formed by the measurement light which emerges from the measurement optical system, is obliquely incident on the mark, passes through the mark and the projection optical system, is obliquely incident on the substrate, is reflected by the substrate, passes through the projection optical system, and returns to the measurement optical system again, and (ii) an image of the mark formed by measurement light which emerges from the measurement optical system, is obliquely incident on the mark, is reflected by the mark, and returns to the measurement optical system again, wherein the control unit calculates the surface position information of the substrate in a direction along an optical axis of the projection optical system, based on an interval between the image of the mark formed by the measurement light which has passed through the mark and the image of the mark formed by the measurement light reflected by the mark.