Method and apparatus for measuring wafer thickness

摘要: A system for non-contact measurement of thickness a test object. laser beam is split into two identical directly opposed input beams. calibration object known causes beams to be reflected from sides the Each passes through sensing means including pinhole aperture and photodiode sensor. Maximum sensor output defines first second focal points distance apart. The removed, inserted path beams, creating focus position intensity curves By determining deviation, at maximum output, positions reflecting surfaces surfaces, can readily accurately determined.