A calibration substrate for use during calibration of a lithographic apparatus is disclosed. The calibration substrate includes a first substantially flat surface, a second substantially flat surface that is substantially parallel to the first surface, and an edge that connects the first surface to the second surface. The calibration substrate has a thermal expansion coefficient of less than about 1.0×10−6 K−1 to reduce deformation thereof due to thermal changes in the substrate while in the lithographic apparatus.