METHOD AND APPARATUS FOR MEASURING SHAPE OR THICKNESS INFORMATION OF A SUBSTRATE

摘要

An interferometer system and method may be used to measure substrate thickness or shape. The system may include two spaced apart reference flats having that form an optical cavity between two parallel reference surfaces. A substrate holder may be configured to place the substrate in the cavity with first and second substrate surfaces substantially parallel with corresponding first and second reference surfaces such that a space between the first or second substrate surface is three millimeters or less from a corresponding one of the reference surfaces or a damping surface. Interferometer devices may be located on diametrically opposite sides of the cavity and optically coupled thereto. The interferometers can map variations in spacing between the substrate surfaces and the reference surfaces, respectively, through interference of light optically coupled to and from to the cavity via the interferometer devices.