| 摘要 |
A pair of optical profile measuring systems 10, 20 are located at positions facing to both surfaces of a wafer 1 vertically supported at its edge. A thickness gauge 50 having one or more sensors is located between the optical systems 10, 20 for measuring thickness at several points on the wafer 1. Each optical system 10, 20 comprises a light emitter 11, 21 for discharging a measuring light beam 12, 22, a collimator lens 14, 24 for rectifying the light beam 12, 22 into a collimated beam, an optical flat 15, 25 for transmitting the collimated light beam 12, 22, a light detector 16, 26 receiving the light beams 12, 22 reflected on a surface of the wafer 1 and on a referential plane of the optical flat 15, 25 through the collimator lens 14, 24 and a computer 17, 27 for processing interference fringes which occur between the surface of the wafer 1 and the referential plane of the optical flat 15, 25. Profiles of main and backside surfaces of the wafer 1 are calculated from interference fringes corresponding to both surfaces of a wafer 1, and a real shape of the wafer 1 is determined from the profiles in consultation with thickness values measured by the thickness gauge 50. |
